Nh compound name

Nh compound name DEFAULT

Nomenclature


Long before chemists knew the formulas for chemical compounds, they developed a system of nomenclature that gave each compound a unique name. Today we often use chemical formulas, such as NaCl, C12H22O11, and Co(NH3)6(ClO4)3, to describe chemical compounds. But we still need unique names that unambiguously identify each compound.


Common Names

Some compounds have been known for so long that a systematic nomenclature cannot compete with well-established common names. Examples of compounds for which common names are used include water (H2O), ammonia (NH3), and methane (CH4).

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Naming Ionic Compounds

(Metals with Non-metals)

The names of ionic compounds are written by listing the name of the positive ion followed by the name of the negative ion.

NaClsodium chloride
(NH4)2SO4ammonium sulfate
NaHCO3sodium bicarbonate

We therefore need a series of rules that allow us to unambiguously name positive and negative ions before we can name the salts these ions form.

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Naming Positive Ions

Monatomic positive ions have the name of the element from which they are formed.

Na+sodium Zn2+zinc
Ca2+calcium H+hydrogen
K+potassium Sr2+strontium

Some metals form positive ions in more than one oxidation state. One of the earliest methods of distinguishing between these ions used the suffixes -ous and -ic added to the Latin name of the element to represent the lower and higher oxidation states, respectively.

Fe2+ferrous Fe3+ferric
Sn2+stannous Sn4+stannic
Cu+cuprous Cu2+cupric

Chemists now use a simpler method, in which the charge on the ion is indicated by a Roman numeral in parentheses immediately after the name of the element.

Fe2+iron(II) Fe3+iron (III)
Sn2+tin(II) Sn4+tin(IV)
Cu+copper(I) Cu2+copper(II)

Polyatomic positive ions often have common names ending with the suffix -onium.

H3O+hydronium
NH4+ammonium

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Naming Negative Ions

Negative ions that consist of a single atom are named by adding the suffix -ide to the stem of the name of the element.

F-fluoride O2-oxide
Cl-chloride S2-sulfide
Br-bromide N3-nitride
I-iodide P3-phosphide
H-hydrideC4-carbide

 

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Common Polyatomic Negative Ions

-1 ions
HCO3-bicarbonateHSO4-hydrogen sulfate (bisulfate)
CH3CO2-acetateClO4-perchlorate
NO3-nitrateClO3-chlorate
NO2-nitrite ClO2-chlorite
MnO4-permanganateClO-hypochlorite
CN-cyanideOH-hydroxide
-2 ions
CO32-carbonateO22-peroxide
SO42-sulfateCrO42-chromate
SO32-sulfite Cr2O72-dichromate
S2O32-thiosulfateHPO42-hydrogen phosphate
-3 ions
PO43-phosphateAsO43-arsenate
BO33-borate

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Naming Polyatomic Ions

At first glance, the nomenclature of the polyatomic negative ions in the table above seems hopeless. There are several general rules, however, that can bring some order out of this apparent chaos.

The name of the ion usually ends in either -ite or -ate. The -ite ending indicates a low oxidation state. Thus,the NO2- ion is the nitrite ion.

The -ate ending indicates a high oxidation state. The NO3- ion, for example, is the nitrate ion.

The prefix hypo- is used to indicate the very lowest oxidation state. The ClO- ion, for example, is the hypochlorite ion.

The prefix per- (as in hyper-) is used to indicate the very highest oxidation state. The ClO4- ion is therefore the perchlorate ion.

There are only a handful of exceptions to these generalizations. The names of the hydroxide (OH-), cyanide (CN-), and peroxide (O22-) ions, for example, have the -ide ending because they were once thought to be monatomic ions.

Practice Problem 5

The bone and tooth enamel in your body contain ionic compounds such as calcium phosphate and hydroxyapatite. Predict the formula of calcium phosphate, which contains Ca2+ and PO43- ions. Calculate the value of x, if the formula of hydroxyapatite is Cax(PO4)3(OH).

Click here to check your answer to Practice Problem 5

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Naming Simple Covalent Compounds

( Non-metals with non-metals )

Oxidation states also play an important role in naming simple covalent compounds. The name of the atom in the positive oxidation state is listed first. The suffix -ide is then added to the stem of the name of the atom in the negative oxidation state.

HCl hydrogen chloride
NO nitrogen oxide
BrCl bromine chloride

As a rule, chemists write formulas in which the element in the positive oxidation state is written first, followed by the element(s) with negative oxidation numbers.

The number of atoms of an element in simple covalent compounds is indicated by adding one of the following Greek prefixes to the name of the element.

1 mono-6 hexa-
2 di-7 hepta-
3 tri- 8 octa-
4 tetra- 9 nona-
5 penta- 10 deca-

The prefix mono- is seldom used because it is redundant. The principal exception to this rule is carbon monoxide (CO).

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Naming Acids

Simple covalent compounds that contain hydrogen, such as HCl, HBr, and HCN, often dissolve in water to produce acids. These solutions are named by adding the prefix hydro- to the name of the compound and then replacing the suffix -ide with -ic. For example, hydrogen chloride (HCl) dissolves in water to form hydrochloric acid; hydrogen bromide (HBr) forms hydrobromic acid; and hydrogen cyanide (HCN) forms hydrocyanic acid.

Many of the oxygen-rich polyatomic negative ions in Table 2.1 form acids that are named by replacing the suffix -ate with -ic and the suffix -ite with -ous.

Acids containing ions ending with ide often become hydro -ic acid
Cl-chlorideHCl hydrochloric acid
F-fluorideHF hydrofluoric acid
S2-sulfideH2S hydrosulfuric acid

Acids containing ions ending with ate usually become -ic acid
CH3CO2-acetate CH3CO2H acetic acid
CO32-carbonate H2CO3carbonic acid
BO33-borate H3BO3boric acid
NO3-nitrate HNO3nitric acid
SO42-sulfate H2SO4sulfuric acid
ClO4-perchlorate HClO4perchloric acid
PO43-phosphate H3PO4phosphoric acid
MnO4-permanganate HMnO4permanganic acid
CrO42-chromate H2CrO4chromic acid
ClO3-chlorate HClO3chloric acid
Acids containing ions ending with ite usually become -ous acid
ClO2-chlorite HClO2chlorous acid
NO2-nitrite HNO2nitrous acid
SO32-sulfite H2SO 3sulfurous acid
ClO-hypochlorite HClO hypochlorous acid

Complex acids can be named by indicating the presence of an acidic hydrogen as follows.

NaHCO3sodium hydrogen carbonate (also known as sodium bicarbonate)
NaHSO3sodium hydrogen sulfite (also known as sodium bisulfite)
KH2PO4potassium dihydrogen phosphate

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Sours: https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch2/names.html

Imidogen

Inorganic radical with the chemical formula NH

Chemical compound

Imidogen is an inorganic compound with the chemical formula NH.[2] Like other simple radicals, it is highly reactive and consequently short-lived except as a dilute gas. Its behavior depends on its spin multiplicity, i.e. the triplet versus singlet ground state.

Production and properties[edit]

Imidogen can be generated by electrical discharge in an atmosphere of ammonia.[3]

Imidogen has a large rotational splitting and a weak spin-spin interaction, therefore it will be less likely to undergo collision-induced Zeeman transitions.[3] Ground-state imidogen can be magnetically trapped using buffer-gas loading from a molecular beam.[3]

The first excited state (a1Δ) has a long lifetime as its relaxation to ground state (X3Σ) is spin-forbidden.[4][5] Imidogen undergoes collision-induced intersystem crossing.[6]

Reactivity[edit]

Ignoring hydrogen atoms, imidogen is isoelectronic with carbene (CH2) and oxygen (O) atoms, and it exhibits comparable reactivity.[4] The first excited state can be detected by laser-induced fluorescence (LIF).[4] LIF methods allow for detection of depletion, production, and chemical products of NH. It reacts with nitric oxide (NO):

NH + NO → N2 + OH
NH + NO → N2O + H

The former reaction is more favorable with a ΔH0 of −408±2 kJ/mol compared to a ΔH0 of −147±2 kJ/mol for the latter reaction.[7]

Nomenclature[edit]

The trivial namenitrene is the preferred IUPAC name. The systematic names, λ1-azane and hydridonitrogen, valid IUPAC names, are constructed according to the substitutive and additive nomenclatures, respectively.

In appropriate contexts, imidogen can be viewed as ammonia with two hydrogen atoms removed, and as such, azylidene may be used as a context-specific systematic name, according to substitutive nomenclature. By default, this name pays no regard to the radicality of the imidogen molecule. Although, in even more specific context, it can also name the non-radical state, whereas the diradical state is named azanediyl.

Astrochemistry[edit]

Interstellar NH was identified in the diffuse clouds toward ζ Persei and HD 27778 from high-resolution high-signal-to-noise spectra of the NH A3Π→X3Σ (0,0) absorption band near 3358 Å.[8] A temperature of about 30 K (−243 °C) favored an efficient production of CN from NH within the diffuse cloud.[9][10][8]

Reactions relevant to astrochemistry[edit]

Reaction Rate constant Rate/[H2]2
N + H → NH + e1×10−93.5×10−18
NH2 + O → NH + OH 2.546×10−131.4×10−13
NH+
2 + e → NH + H
3.976×10−72.19×10−21
NH+
3 + e → NH + H + H
8.49×10−72.89×10−19
NH + N → N2 + H 4.98×10−114.36×10−16
NH + O → OH + N 1.16×10−111.54×10−14
NH + C+ → CN+ + H 7.8×10−104.9×10−19
NH + H3+ → NH+
2 + H2
1.3×10−93.18×10−19
NH + H+ → NH+ + H 2.1×10−94.05×10−20

Within diffuse clouds H + N → NH + e is a major formation mechanism. Near chemical equilibrium important NH formation mechanisms are recombinations of NH+
2 and NH+
3 ions with electrons. Depending on the radiation field in the diffuse cloud, NH2 can also contribute.

NH is destroyed in diffuse clouds by photodissociation and photoionization. In dense clouds NH is destroyed by reactions with atomic oxygen and nitrogen. O+ and N+ form OH and NH in diffuse clouds. NH is involved in creating N2, OH, H, CN+, CH, N, NH+
2, NH+ for the interstellar medium.

NH has been reported in the diffuse interstellar medium but not in dense molecular clouds.[13] The purpose of detecting NH is often to get a better estimate of the rotational constants and vibrational levels of NH.[14] It is also needed in order to confirm theoretical data which predicts N and NH abundances in stars which produce N and NH and other stars with leftover trace amounts of N and NH.[15] Using current values for rotational constants and vibrations of NH as well as those of OH and CH permit studying the carbon, nitrogen and oxygen abundances without resorting to a full spectrum synthesis with a 3D model atmosphere.[16]

See also[edit]

References[edit]

  1. ^IUPAC Red Book 2005
  2. ^Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN .
  3. ^ abcCampbell, W. C.; Tsikata, E.; van Buuren, L.; Lu, H.; Doyle, J. M. (2007). "Magnetic Trapping and Zeeman Relaxation of NH (X3Σ)". Physical Review Letters. 98 (21): 213001. arXiv:physics/0702071. doi:10.1103/PhysRevLett.98.213001.
  4. ^ abcHack, W.; Rathmann, K. (1990). "Elementary reaction of imidogen (a1Δ) with carbon monoxide". Journal of Physical Chemistry. 94 (9): 3636–3639. doi:10.1021/j100372a050.
  5. ^National Institute of Standards and Technology[full citation needed]
  6. ^Adams, J. S.; Pasternack, L. (1991). "Collision-induced intersystem crossing in imidogen (a1Δ) → imidogen (X3Σ)". Journal of Physical Chemistry. 95 (8): 2975–2982. doi:10.1021/j100161a009.
  7. ^Patel-Misra, D.; Dagdigian, P. J. (1992). "Dynamics of the imidogen (X3Σ) + nitric oxide (X2Π) reaction: internal state distribution of the hydroxyl (X2Π) product". Journal of Physical Chemistry. 96 (8): 3232–3236. doi:10.1021/j100187a011.
  8. ^ abMeyer, David M.; Roth, Katherine C. (August 1, 1991). "Discovery of interstellar NH". Astrophysical Journal. 376: L49–L52. Bibcode:1991ApJ...376L..49M. doi:10.1086/186100.
  9. ^Wagenblast, R.; Williams, D. A.; Millar, T. J.; Nejad, L. A. M. (1993). "On the origin of NH in diffuse interstellar clouds". Monthly Notices of the Royal Astronomical Society. 260 (2): 420–424. Bibcode:1993MNRAS.260..420W. doi:10.1093/mnras/260.2.420.
  10. ^Crutcher, R. M.; Watson, W. D. (1976). "Upper limit and significance of the NH molecule in diffuse interstellar clouds". Astrophysical Journal. 209 (1): 778–781. Bibcode:1976ApJ...209..778C. doi:10.1086/154775.
  11. ^Prasad, S. S.; Huntress, W. T. (1980). "A model for gas phase chemistry in interstellar clouds. I. The basic model, library of chemical reactions, and chemistry among C, N, and O compounds". Astrophysical Journal Supplement Series. 43: 1. Bibcode:1980ApJS...43....1P. doi:10.1086/190665.
  12. ^"The UMIST Database for Astrochemistry 2012/ astrochemistry.net".
  13. ^Cernicharo, José; Goicoechea, Javier R.; Caux, Emmanuel (2000). "Far-infrared Detection of C3 in Sagittarius B2 and IRC +10216". Astrophysical Journal Letters. 534 (2): L199–L202. Bibcode:2000ApJ...534L.199C. doi:10.1086/312668. hdl:10261/192089. ISSN 1538-4357.
  14. ^Ram, R. S.; Bernath, P. F.; Hinkle, K. H. (1999). "Infrared emission spectroscopy of NH: Comparison of a cryogenic echelle spectrograph with a Fourier transform spectrometer". The Journal of Chemical Physics. 110 (12): 5557. Bibcode:1999JChPh.110.5557R. doi:10.1063/1.478453.
  15. ^Grevesse, N.; Lambert, D. L.; Sauval, A. J.; Van Dishoeck, E. F.; Farmer, C. B.; Norton, R. H. (1990). "Identification of solar vibration-rotation lines of NH and the solar nitrogen abundance". Astronomy and Astrophysics. 232 (1): 225. Bibcode:1990A&A...232..225G. ISSN 0004-6361.
  16. ^Frebel, Anna; Collet, Remo; Eriksson, Kjell; Christlieb, Norbert; Aoki, Wako (2008). "HE 1327–2326, an Unevolved Star with [Fe/H] < –5.0. II. New 3D–1D Corrected Abundances from a Very Large Telescope UVES Spectrum". Astrophysical Journal. 684 (1): 588–602. arXiv:0805.3341. Bibcode:2008ApJ...684..588F. doi:10.1086/590327. ISSN 0004-637X.

External links[edit]

  • Buchowiecki, Marcin (28 January 2021). "Uncertainty of High Temperature Heat Capacities: The Case Study of the NH Radical". The Journal of Physical Chemistry A. 125 (3): 795–800. doi:10.1021/acs.jpca.0c09512.
Sours: https://en.wikipedia.org/wiki/Imidogen
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Learning Objective

  • Give examples of applications of nitrogen compounds.

Key Points

    • Nitrogen oxides, called NOxcompounds, are important for their explosive properties. These properties are determined by the extremely strong and stable bond found in molecular, diatomic nitrogen, N2, which has a bond dissociation energy of 945 kJ/mol (226 kcal/mol).
    • The main neutral hydride of nitrogen is ammonia (NH3), which has a pKb of 9.2, and is thus a weak base. The corresponding deprotonated species, NH2, is called an amide and is a strong base (because it’s the conjugate base of ammonia, whose pKa is around 38).
    • Nitrogen is a constituent of molecules in every major drug class in pharmacology and medicine, from antibiotics to neurotransmitters and beyond. One important aspect of nitrogen is that it is the only non-metal that can maintain a positive charge at physiological pH.

Terms

  • propellantFuel, oxidizer, reaction mass or mixture for one or more engines (especially internal combustion engines or jet engines) that is carried within a vehicle prior to use.
  • oxideA binary chemical compound of oxygen with another chemical element.
  • anionA negatively charged ion, as opposed to a cation.
  • bond dissociation energyThe energy required to separate two atoms joined by a particular bond. Expressed in terms of a mole of such bonded atoms. Indicates the strength of the bond.

Survey of Nitrogen Compounds and their Uses

Nitrogen compounds play an important role in many aspects of life and commercial processes, from the industrial production of fertilizers to the building blocks of life.

The nitrogen-nitrogen triple bond in N2 contains 226 kcal/mol of energy, making it one of the strongest bonds known. When nitrogen gas is formed as a product from various reactions, the bond energy associated with the N-N triple bond is released, causing the explosive properties seen in many nitrogen compounds.

Amines

The main neutral hydride of nitrogen is ammonia (NH3), although hydrazine (N2H4) is also commonly used. Ammonia is more basic than water by 6 orders of magnitude. In solution, ammonia forms the ammonium ion (NH4+). The pKa of ammonium chloride is 9.2. Liquid ammonia (boiling point 240 K) is amphiprotic (displaying either Brønsted-Lowry acidic or basic character) and forms ammonium and the less common amide ions (NH2). Ammonia has a pKa of 38, making the corresponding amide ions very strong bases. Singly, doubly, triply and quadruply substituted alkyl compounds of ammonia are called amines (four substitutions, to form commercially and biologically important quaternary amines, results in a positively charged nitrogen, and thus a water-soluble compound).

Azides

Other classes of nitrogen anions (negatively charged ions) are the poisonous azides (N3), which are linear and isoelectronic to carbon dioxide, but which bind to important iron-containing enzymes in the body in a manner resembling cyanide.

Nitrogen Oxides

Another molecule of the same structure is the colorless and relatively inert anesthetic gas nitrous oxide (dinitrogen monoxide, N2O), also known as laughing gas. This is one of a variety of nitrogen oxides that form a family often abbreviated as NOx. Nitric oxide (nitrogen monoxide, NO), is a natural free radical used in signal transduction in both plants and animals. The reddish and poisonous nitrogen dioxide (NO2) contains an unpaired electron and is an important component of smog. Nitrogen molecules containing unpaired electrons show a tendency to dimerize (thus pairing the electrons), and are, in general, highly reactive. The corresponding acids are nitrous (HNO2) and nitric acid (HNO3), with the corresponding salts called nitrites and nitrates.

Nitrogen Compounds used as Explosives and Propellants

One of the earliest uses of a nitrogen compound as an explosive was potassium nitrate, also called saltpeter, used in gunpowder. This is a mixture of potassium nitrate, carbon and sulfur. When the mixture is ignited in an enclosed space, such as a gun-barrel or a firework, the nitrate ions oxidize the carbon and sulfur in a highly exothermic reaction, producing high-temperature gases very rapidly. This can propel a bullet out of a gun or cause a firework to explode.

The higher oxides, dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4) and dinitrogen pentoxide (N2O5), are unstable and explosive, a consequence of the chemical stability of N2. Nearly every hypergolic (i.e. not requiring ignition) rocket engine uses N2O4 as the oxidizer; their fuels, various forms of hydrazine, are also nitrogen compounds.

These engines were extensively used on spacecraft such as the space shuttle and those of the Apollo Program because their propellants are liquids at room temperature and ignition occurs on contact without an ignition system, allowing many precisely controlled burns. N2O4 is an intermediate in the manufacture of nitric acid HNO3, one of the few acids stronger than the hydronium ion, and a fairly strong oxidizing agent.

Nitrogen is notable for the range of explosively unstable compounds that it can produce. Nitrogen triiodide (NI3) is an extremely sensitive contact explosive. Nitrocellulose, produced by nitration of cellulose with nitric acid, is also known as guncotton. Nitroglycerin, made by nitration of glycerin, is the dangerously unstable explosive ingredient of dynamite. The comparatively stable, but less powerful explosive trinitrotoluene (TNT) is the standard explosive against which the power of nuclear explosions are measured. In all cases, the explosive properties of nitrogen compounds are derived from the extreme stability of the product of these reactions: gaseous molecular nitrogen, N2.

Nitrogen Compounds in Drugs and Medicine

Nitrogen is a constituent of molecules in every major drug class in pharmacology and medicine. Nitric oxide (NO) has recently been discovered to be an important signaling molecule in physiology. Nitrous oxide (N2O) was discovered early in the 19th century to be a partial anesthetic, though it was not used as a surgical anesthetic until later. Called “laughing gas,” it was found to induce a state of social disinhibition resembling drunkenness.

Other notable nitrogen-containing drugs are drugs derived from plant alkaloids, such as morphine. Many alkaloids are known to have pharmacological effects; in some cases, they appear as natural chemical defenses of plants against predation. Drugs that contain nitrogen include all major classes of antibiotics, and organic nitrate drugs like nitroglycerin and nitroprusside that regulate blood pressure and heart action. Amines (alkyl derivatives of nitrogen) are important in pharmacology because they can readily carry a positive charge, as the corresponding protonated ammonium species. This allows for electrostatic interactions between the ammonium cation and various negatively charged or polarizable species in proteins.

 

Sours: https://courses.lumenlearning.com/introchem/chapter/nitrogen-compounds/
Naming Amines - IUPAC Nomenclature \u0026 Common Names

Formation of simple nitrogen hydrides NH and NH2 at cryogenic temperatures through N + NH3 → NH + NH2 reaction: dark cloud chemistry of nitrogen

S. Nourry and L. Krim, Phys. Chem. Chem. Phys., 2016, 18, 18493 DOI: 10.1039/C6CP01621A

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Compound name nh

Nihonium

Nihonium is the temporary name of a chemical element in the periodic table that has the temporary symbol Nh and has the atomic number 113. It was discovered from the bombardment of atoms of Americium-243 with ions of calcium-48. Among the product of the bombardment were four atoms of ununpentium which in less than 1/10 second decayed into atoms of ununtritium. On September 2004 a team of Japanese scientists declared that they succeeded in synthesizing the element.

It is expected to have properties similar of thallium and indium.

Applications

Ununtritium does not have any known application and little is known about it.

Ununtritium in the environment

Ununtritium is not found free in the environment, since it is a synthetic element.

Health effects of Nihonium

As it is so unstable, any amount formed would decompose to other elements so quickly that there’s no reason to study its effects on human health.

Environmental effects of Nihonium

Due to its extremely short half-life, there’s no reason for considering the effects of ununtritium in the environment.

Back to chart periodic elements

Sours: https://www.lenntech.com/periodic/elements/uut.htm
[Download PDF] Common Names of Chemical Compounds -- SSC Exam 2017

Nihonium

chemical element 113

Chemical element, symbol Nh and atomic number 113

Pronunciation ​(nih-HOH-nee-əm)
Mass number[286]
Atomic number(Z)113
Groupgroup 13 (boron group)
Periodperiod 7
Block p-block
Electron configuration[Rn] 5f14 6d10 7s2 7p1 (predicted)[1]
Electrons per shell2, 8, 18, 32, 32, 18, 3 (predicted)
Phaseat STPsolid (predicted)[1][2][3]
Melting point700 K ​(430 °C, ​810 °F) (predicted)[1]
Boiling point1430 K ​(1130 °C, ​2070 °F) (predicted)[1][4]
Density (near r.t.)16 g/cm3 (predicted)[4]
Heat of fusion7.61 kJ/mol (extrapolated)[3]
Heat of vaporisation130 kJ/mol (predicted)[2][4]
Oxidation states(−1), (+1), (+3), (+5) (predicted)[1][4][5]
Ionisation energies
Atomic radiusempirical: 170 pm (predicted)[1]
Covalent radius172–180 pm (extrapolated)[3]
Natural occurrencesynthetic
Crystal structure ​hexagonal close-packed (hcp)
Hexagonal close-packed crystal structure for nihonium

(predicted)[6][7]
CAS Number54084-70-7
NamingAfter Japan (Nihon in Japanese)
DiscoveryRiken (Japan, first undisputed claim 2004)
JINR (Russia) and Livermore (US, first announcement 2003)
Category Category: Nihonium
| references

Nihonium is a syntheticchemical element with the symbolNh and atomic number 113. It is extremely radioactive; its most stable known isotope, nihonium-286, has a half-life of about 10 seconds. In the periodic table, nihonium is a transactinide element in the p-block. It is a member of period 7 and group 13 (boron group).

Nihonium was first reported to have been created in 2003 by a Russian–American collaboration at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, and in 2004 by a team of Japanese scientists at Riken in Wakō, Japan. The confirmation of their claims in the ensuing years involved independent teams of scientists working in the United States, Germany, Sweden, and China, as well as the original claimants in Russia and Japan. In 2015, the IUPAC/IUPAP Joint Working Party recognised the element and assigned the priority of the discovery and naming rights for the element to Riken. The Riken team suggested the name nihonium in 2016, which was approved in the same year. The name comes from the common Japanese name for Japan (日本, nihon).

Very little is known about nihonium, as it has only been made in very small amounts that decay within seconds. The anomalously long lives of some superheavy nuclides, including some nihonium isotopes, are explained by the "island of stability" theory. Experiments support the theory, with the half-lives of the confirmed nihonium isotopes increasing from milliseconds to seconds as neutrons are added and the island is approached. Nihonium has been calculated to have similar properties to its homologues boron, aluminium, gallium, indium, and thallium. All but boron are post-transition metals, and nihonium is expected to be a post-transition metal as well. It should also show several major differences from them; for example, nihonium should be more stable in the +1 oxidation state than the +3 state, like thallium, but in the +1 state nihonium should behave more like silver and astatine than thallium. Preliminary experiments in 2017 showed that elemental nihonium is not very volatile; its chemistry remains largely unexplored.

Introduction[edit]

This section is transcluded from Introduction to the heaviest elements. (edit | history)

See also: Superheavy element § Introduction

A graphic depiction of a nuclear fusion reaction
A graphic depiction of a nuclear fusionreaction. Two nuclei fuse into one, emitting a neutron. Thus far, reactions that created new elements were similar, with the only possible difference that several singular neutrons sometimes were released, or none at all.

The heaviest[a]atomic nuclei are created in nuclear reactions that combine two other nuclei of unequal size[b] into one; roughly, the more unequal the two nuclei in terms of mass, the greater the possibility that the two react.[16] The material made of the heavier nuclei is made into a target, which is then bombarded by the beam of lighter nuclei. Two nuclei can only fuse into one if they approach each other closely enough; normally, nuclei (all positively charged) repel each other due to electrostatic repulsion. The strong interaction can overcome this repulsion but only within a very short distance from a nucleus; beam nuclei are thus greatly accelerated in order to make such repulsion insignificant compared to the velocity of the beam nucleus.[17] Coming close alone is not enough for two nuclei to fuse: when two nuclei approach each other, they usually remain together for approximately 10−20 seconds and then part ways (not necessarily in the same composition as before the reaction) rather than form a single nucleus.[17][18] If fusion does occur, the temporary merger—termed a compound nucleus—is an excited state. To lose its excitation energy and reach a more stable state, a compound nucleus either fissions or ejects one or several neutrons,[c] which carry away the energy. This occurs in approximately 10−16 seconds after the initial collision.[19][d]

The beam passes through the target and reaches the next chamber, the separator; if a new nucleus is produced, it is carried with this beam.[22] In the separator, the newly produced nucleus is separated from other nuclides (that of the original beam and any other reaction products)[e] and transferred to a surface-barrier detector, which stops the nucleus. The exact location of the upcoming impact on the detector is marked; also marked are its energy and the time of the arrival.[22] The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long. The nucleus is recorded again once its decay is registered, and the location, the energy, and the time of the decay are measured.[22]

Stability of a nucleus is provided by the strong interaction. However, its range is very short; as nuclei become larger, their influence on the outermost nucleons (protons and neutrons) weakens. At the same time, the nucleus is torn apart by electrostatic repulsion between protons, as it has unlimited range. Nuclei of the heaviest elements are thus theoretically predicted[27] and have so far been observed to primarily decay via decay modes that are caused by such repulsion: alpha decay and spontaneous fission;[f] these modes are predominant for nuclei of superheavy elements. Alpha decays are registered by the emitted alpha particles, and the decay products are easy to determine before the actual decay; if such a decay or a series of consecutive decays produces a known nucleus, the original product of a reaction can be determined arithmetically.[g] Spontaneous fission, however, produces various nuclei as products, so the original nuclide cannot be determined from its daughters.[h]

The information available to physicists aiming to synthesize one of the heaviest elements is thus the information collected at the detectors: location, energy, and time of arrival of a particle to the detector, and those of its decay. The physicists analyze this data and seek to conclude that it was indeed caused by a new element and could not have been caused by a different nuclide than the one claimed. Often, provided data is insufficient for a conclusion that a new element was definitely created and there is no other explanation for the observed effects; errors in interpreting data have been made.[i]

History[edit]

See also: Discoveries of the chemical elements

Early indications[edit]

The syntheses of elements 107 to 112 were conducted at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, from 1981 to 1996. These elements were made by cold fusion[j] reactions, in which targets made of thallium, lead, and bismuth, which are around the stable configuration of 82 protons, are bombarded with heavy ions of period 4 elements. This creates fused nuclei with low excitation energies due to the stability of the targets' nuclei, significantly increasing the yield of superheavy elements. Cold fusion was pioneered by Yuri Oganessian and his team in 1974 at the Joint Institute for Nuclear Research (JINR) in Dubna, Soviet Union. Yields from cold fusion reactions were found to decrease significantly with increasing atomic number; the resulting nuclei were severely neutron-deficient and short-lived. The GSI team attempted to synthesise element 113 via cold fusion in 1998 and 2003, bombarding bismuth-209 with zinc-70; both attempts were unsuccessful.[43][44]

Faced with this problem, Oganessian and his team at the JINR turned their renewed attention to the older hot fusion technique, in which heavy actinide targets were bombarded with lighter ions. Calcium-48 was suggested as an ideal projectile, because it is very neutron-rich for a light element (combined with the already neutron-rich actinides) and would minimise the neutron deficiencies of the nuclides produced. Being doubly magic, it would confer benefits in stability to the fused nuclei. In collaboration with the team at the Lawrence Livermore National Laboratory (LLNL) in Livermore, California, United States, they made an attempt on element 114 (which was predicted to be a magic number, closing a proton shell, and more stable than element 113).[43]

In 1998, the JINR–LLNL collaboration started their attempt on element 114, bombarding a target of plutonium-244 with ions of calcium-48:[43]

244
94Pu
+ 48
20Ca
292114* → 290114 + 2
n
+ e290113 + νe

A single atom was observed which was thought to be the isotope 289114: the results were published in January 1999.[45] Despite numerous attempts to repeat this reaction, an isotope with these decay properties has never again been found, and the exact identity of this activity is unknown.[46] A 2016 paper considered that the most likely explanation of the 1998 result is that two neutrons were emitted by the produced compound nucleus, leading to 290114 and electron capture to 290113, while more neutrons were emitted in all other produced chains. This would have been the first report of a decay chain from an isotope of element 113, but it was not recognised at the time, and the assignment is still uncertain.[9] A similar long-lived activity observed by the JINR team in March 1999 in the 242Pu + 48Ca reaction may be due to the electron-capture daughter of 287114, 287113; this assignment is also tentative.[8]

JINR–LLNL collaboration[edit]

The now-confirmed discovery of element 114 was made in June 1999 when the JINR team repeated the first 244Pu + 48Ca reaction from 1998;[47][48] following this, the JINR team used the same hot fusion technique to synthesise elements 116 and 118 in 2000 and 2002 respectively via the 248Cm + 48Ca and 249Cf + 48Ca reactions. They then turned their attention to the missing odd-numbered elements, as the odd protons and possibly neutrons would hinder decay by spontaneous fission and result in longer decay chains.[43][49]

The first report of element 113 was in August 2003, when it was identified as an alpha decay product of element 115. Element 115 had been produced by bombarding a target of americium-243 with calcium-48 projectiles. The JINR–LLNL collaboration published its results in February 2004:[49]

243
95Am
+ 48
20Ca
291115* → 288115 + 3
n
284113 +
α
243
95Am
+ 48
20Ca
291115* → 287115 + 4
n
283113 +
α

Four further alpha decays were observed, ending with the spontaneous fission of isotopes of element 105, dubnium.[49]

Riken[edit]

While the JINR–LLNL collaboration had been studying fusion reactions with 48Ca, a team of Japanese scientists at the Riken Nishina Center for Accelerator-Based Science in Wakō, Japan, led by Kōsuke Morita had been studying cold fusion reactions. Morita had previously studied the synthesis of superheavy elements at the JINR before starting his own team at Riken. In 2001, his team confirmed the GSI's discoveries of elements 108, 110, 111, and 112. They then made a new attempt on element 113, using the same 209Bi + 70Zn reaction that the GSI had attempted unsuccessfully in 1998. Despite the much lower yield expected than for the JINR's hot fusion technique with calcium-48, the Riken team chose to use cold fusion as the synthesised isotopes would alpha decay to known daughter nuclides and make the discovery much more certain, and would not require the use of radioactive targets.[50] In particular, the isotope 278113 expected to be produced in this reaction would decay to the known 266Bh, which had been synthesised in 2000 by a team at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley.[51]

The bombardment of 209Bi with 70Zn at Riken began in September 2003.[52] The team detected a single atom of 278113 in July 2004 and published their results that September:[53]

209
83Bi
+ 70
30Zn
279113* → 278113 +
n

The Riken team observed four alpha decays from 278113, creating a decay chain passing through 274Rg, 270Mt, and 266Bh before terminating with the spontaneous fission of 262Db.[53] The decay data they observed for the alpha decay of 266Bh matched the 2000 data, lending support for their claim. Spontaneous fission of its daughter 262Db had not been previously known; the American team had observed only alpha decay from this nuclide.[51]

Road to confirmation[edit]

When the discovery of a new element is claimed, the Joint Working Party (JWP) of the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP) assembles to examine the claims according to their criteria for the discovery of a new element, and decides scientific priority and naming rights for the elements. According to the JWP criteria, a discovery must demonstrate that the element has an atomic number different from all previously observed values. It should also preferably be repeated by other laboratories, although this requirement has been waived where the data is of very high quality. Such a demonstration must establish properties, either physical or chemical, of the new element and establish that they are those of a previously unknown element. The main techniques used to demonstrate atomic number are cross-reactions (creating claimed nuclides as parents or daughters of other nuclides produced by a different reaction) and anchoring decay chains to known daughter nuclides. For the JWP, priority in confirmation takes precedence over the date of the original claim. Both teams set out to confirm their results by these methods.[54]

Summary of decay chains passing through isotopes of element 113, ending at mendelevium(element 101) or earlier. The two chains with bold-bordered nuclides were accepted by the JWP as evidence for the discoveries of element 113 and its parents, elements 115 and 117.

2004–2008[edit]

In June 2004 and again in December 2005, the JINR–LLNL collaboration strengthened their claim for the discovery of element 113 by conducting chemical experiments on 268Db, the final decay product of 288115. This was valuable as none of the nuclides in this decay chain were previously known, so that their claim was not supported by any previous experimental data, and chemical experimentation would strengthen the case for their claim, since the chemistry of dubnium is known. 268Db was successfully identified by extracting the final decay products, measuring spontaneous fission (SF) activities and using chemical identification techniques to confirm that they behave like a group 5 element (dubnium is known to be in group 5).[1][55] Both the half-life and decay mode were confirmed for the proposed 268Db which lends support to the assignment of the parent and daughter nuclei to elements 115 and 113 respectively.[55][56] Further experiments at the JINR in 2005 confirmed the observed decay data.[51]

In November and December 2004, the Riken team studied the 205Tl + 70Zn reaction, aiming the zinc beam onto a thallium rather than a bismuth target, in an effort to directly produce 274Rg in a cross-bombardment as it is the immediate daughter of 278113. The reaction was unsuccessful, as the thallium target was physically weak compared to the more commonly used lead and bismuth targets, and it deteriorated significantly and became non-uniform in thickness. The reasons for this weakness are unknown, given that thallium has a higher melting point than bismuth.[57] The Riken team then repeated the original 209Bi + 70Zn reaction and produced a second atom of 278113 in April 2005, with a decay chain that again terminated with the spontaneous fission of 262Db. The decay data were slightly different from those of the first chain: this could have been because an alpha particle escaped from the detector without depositing its full energy, or because some of the intermediate decay products were formed in metastable isomeric states.[51]

In 2006, a team at the Heavy Ion Research Facility in Lanzhou, China, investigated the 243Am + 26Mg reaction, producing four atoms of 266Bh. All four chains started with an alpha decay to 262Db; three chains ended there with spontaneous fission, as in the 278113 chains observed at Riken, while the remaining one continued via another alpha decay to 258Lr, as in the 266Bh chains observed at LBNL.[54]

In June 2006, the JINR–LLNL collaboration claimed to have synthesised a new isotope of element 113 directly by bombarding a neptunium-237 target with accelerated calcium-48 nuclei:

237
93Np
+ 48
20Ca
285113* → 282113 + 3
n

Two atoms of 282113 were detected. The aim of this experiment had been to synthesise the isotopes 281113 and 282113 that would fill in the gap between isotopes produced via hot fusion (283113 and 284113) and cold fusion (278113). After five alpha decays, these nuclides would reach known isotopes of lawrencium, assuming that the decay chains were not terminated prematurely by spontaneous fission. The first decay chain ended in fission after four alpha decays, presumably originating from 266Db or its electron-capture daughter 266Rf. Spontaneous fission was not observed in the second chain even after four alpha decays. A fifth alpha decay in each chain could have been missed, since 266Db can theoretically undergo alpha decay, in which case the first decay chain would have ended at the known 262Lr or 262No and the second might have continued to the known long-lived 258Md, which has a half-life of 51.5 days, longer than the duration of the experiment: this would explain the lack of a spontaneous fission event in this chain. In the absence of direct detection of the long-lived alpha decays, these interpretations remain unconfirmed, and there is still no known link between any superheavy nuclides produced by hot fusion and the well-known main body of the chart of nuclides.[58]

2009–2015[edit]

The JWP published its report on elements 113–116 and 118 in 2011. It recognised the JINR–LLNL collaboration as having discovered elements 114 and 116, but did not accept either team's claim to element 113 and did not accept the JINR–LLNL claims to elements 115 and 118. The JINR–LLNL claim to elements 115 and 113 had been founded on chemical identification of their daughter dubnium, but the JWP objected that current theory could not distinguish between superheavy group 4 and group 5 elements by their chemical properties with enough confidence to allow this assignment.[51] The decay properties of all the nuclei in the decay chain of element 115 had not been previously characterised before the JINR experiments, a situation which the JWP generally considers "troublesome, but not necessarily exclusive", and with the small number of atoms produced with neither known daughters nor cross-reactions the JWP considered that their criteria had not been fulfilled.[51] The JWP did not accept the Riken team's claim either due to inconsistencies in the decay data, the small number of atoms of element 113 produced, and the lack of unambiguous anchors to known isotopes.[51]

In early 2009, the Riken team synthesised the decay product 266Bh directly in the 248Cm + 23Na reaction to establish its link with 278113 as a cross-bombardment. They also established the branched decay of 262Db, which sometimes underwent spontaneous fission and sometimes underwent the previously known alpha decay to 258Lr.[59][60]

In late 2009, the JINR–LLNL collaboration studied the 249Bk + 48Ca reaction in an effort to produce element 117, which would decay to elements 115 and 113 and bolster their claims in a cross-reaction. They were now joined by scientists from Oak Ridge National Laboratory (ORNL) and Vanderbilt University, both in Tennessee, United States,[43] who helped procure the rare and highly radioactive berkelium target necessary to complete the JINR's calcium-48 campaign to synthesise the heaviest elements on the periodic table.[43] Two isotopes of element 117 were synthesised, decaying to element 115 and then element 113:[61]

249
97Bk
+ 48
20Ca
297117* → 294117 + 3
n
290115 + α → 286113 + α
249
97Bk
+ 48
20Ca
297117* → 293117 + 4
n
289115 + α → 285113 + α

The new isotopes 285113 and 286113 produced did not overlap with the previously claimed 282113, 283113, and 284113, so this reaction could not be used as a cross-bombardment to confirm the 2003 or 2006 claims.[54]

In March 2010, the Riken team again attempted to synthesise 274Rg directly through the 205Tl + 70Zn reaction with upgraded equipment; they failed again and abandoned this cross-bombardment route.[57]

After 450 more days of irradiation of bismuth with zinc projectiles, Riken produced and identified another 278113 atom in August 2012.[62] Although electricity prices had soared since the 2011 Tōhoku earthquake and tsunami, and Riken had ordered the shutdown of the accelerator programs to save money, Morita's team was permitted to continue with one experiment, and they chose their attempt to confirm their synthesis of element 113.[63] In this case, a series of six alpha decays was observed, leading to an isotope of mendelevium:

278113 → 274
111Rg
+
α
270
109Mt
+
α
266
107Bh
+
α
262
105Db
+
α
258
103Lr
+
α
254
101Md
+
α

This decay chain differed from the previous observations at Riken mainly in the decay mode of 262Db, which was previously observed to undergo spontaneous fission, but in this case instead alpha decayed; the alpha decay of 262Db to 258Lr is well-known. The team calculated the probability of accidental coincidence to be 10−28, or totally negligible.[62] The resulting 254Md atom then underwent electron capture to 254Fm, which underwent the seventh alpha decay in the chain to the long-lived 250Cf, which has a half-life of around thirteen years.[64]

The 249Bk + 48Ca experiment was repeated at the JINR in 2012 and 2013 with consistent results, and again at the GSI in 2014.[54] In August 2013, a team of researchers at Lund University in Lund, Sweden, and at the GSI announced that they had repeated the 2003 243Am + 48Ca experiment, confirming the findings of the JINR–LLNL collaboration.[52][65] The same year, the 2003 experiment had been repeated at the JINR, now also creating the isotope 289115 that could serve as a cross-bombardment for confirming their discovery of the element 117 isotope 293117, as well as its daughter 285113 as part of its decay chain.[54] Confirmation of 288115 and its daughters was published by the team at the LBNL in 2015.[66]

Approval of discoveries[edit]

In December 2015, the conclusions of a new JWP report were published by IUPAC in a press release, in which element 113 was awarded to Riken; elements 115, 117, and 118 were awarded to the collaborations involving the JINR.[67] A joint 2016 announcement by IUPAC and IUPAP had been scheduled to coincide with the publication of the JWP reports, but IUPAC alone decided on an early release because the news of Riken being awarded credit for element 113 had been leaked to Japanese newspapers.[68] For the first time in history, a team of Asian physicists would name a new element.[67] The JINR considered the awarding of element 113 to Riken unexpected, citing their own 2003 production of elements 115 and 113, and pointing to the precedents of elements 103, 104, and 105 where IUPAC had awarded joint credit to the JINR and LBNL. They stated that they respected IUPAC's decision, but reserved determination of their position for the official publication of the JWP reports.[69]

The full JWP reports were published in January 2016. The JWP recognised the discovery of element 113, assigning priority to Riken. They noted that while the individual decay energies of each nuclide in the decay chain of 278113 were inconsistent, their sum was now confirmed to be consistent, strongly suggesting that the initial and final states in 278113 and its daughter 262Db were the same for all three events. The decay of 262Db to 258Lr and 254Md was previously known, firmly anchoring the decay chain of 278113 to known regions of the chart of nuclides. The JWP considered that the JINR–LLNL collaborations of 2004 and 2007, producing element 113 as the daughter of element 115, did not meet the discovery criteria as they had not convincingly determined the atomic numbers of their nuclides through cross-bombardments, which were considered necessary since their decay chains were not anchored to previously known nuclides. They also considered that the previous JWP's concerns over their chemical identification of the dubnium daughter had not been adequately addressed. The JWP recognised the JINR–LLNL–ORNL–Vanderbilt collaboration of 2010 as having discovered elements 117 and 115, and accepted that element 113 had been produced as their daughter, but did not give this work shared credit.[54][57][70]

After the publication of the JWP reports, Sergey Dimitriev, the lab director of the Flerov lab at the JINR where the discoveries were made, remarked that he was happy with IUPAC's decision, mentioning the time Riken spent on their experiment and their good relations with Morita, who had learnt the basics of synthesising superheavy elements at the JINR.[43][69]

The sum argument advanced by the JWP in the approval of the discovery of element 113 was later criticised in a May 2016 study from Lund University and the GSI, as it is only valid if no gamma decay or internal conversion takes place along the decay chain, which is not likely for odd nuclei, and the uncertainty of the alpha decay energies measured in the 278113 decay chain was not small enough to rule out this possibility. If this is the case, similarity in lifetimes of intermediate daughters becomes a meaningless argument, as different isomers of the same nuclide can have different half-lives: for example, the ground state of 180Ta has a half-life of hours, but an excited state 180mTa has never been observed to decay. This study found reason to doubt and criticise the IUPAC approval of the discoveries of elements 115 and 117, but the data from Riken for element 113 was found to be congruent, and the data from the JINR team for elements 115 and 113 to probably be so, thus endorsing the IUPAC approval of the discovery of element 113.[71][72] Two members of the JINR team published a journal article rebutting these criticisms against the congruence of their data on elements 113, 115, and 117 in June 2017.[73]

Naming[edit]

Using Mendeleev's nomenclature for unnamed and undiscovered elements, nihonium would be known as eka-thallium. In 1979, IUPAC published recommendations according to which the element was to be called ununtrium (with the corresponding symbol of Uut),[74] a systematic element name as a placeholder, until the discovery of the element is confirmed and a name is decided on. The recommendations were widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, but were mostly ignored among scientists in the field, who called it "element 113", with the symbol of E113, (113), or even simply 113.[1]

Before the JWP recognition of their priority, the Japanese team had unofficially suggested various names: japonium, after their home country;[75]nishinanium, after Japanese physicist Yoshio Nishina, the "founding father of modern physics research in Japan";[76] and rikenium, after the institute.[75] After the recognition, the Riken team gathered in February 2016 to decide on a name. Morita expressed his desire for the name to honour the fact that element 113 had been discovered in Japan. Japonium was considered, making the connection to Japan easy to identify for non-Japanese, but it was rejected as Jap is considered an ethnic slur. The name nihonium was chosen after an hour of deliberation: it comes from nihon (日本), one of the two Japanese pronunciations for the name of Japan.[77] The discoverers also intended to reference the support of their research by the Japanese people (Riken being almost entirely government-funded),[78] recover lost pride and trust in science among those who were affected by the Fukushima Daiichi nuclear disaster,[79] and honour Japanese chemist Masataka Ogawa's 1908 discovery of rhenium, which he named "nipponium" with symbol Np after the other Japanese pronunciation of Japan's name.[70] As Ogawa's claim had not been accepted, the name "nipponium" could not be reused for a new element, and its symbol Np had since been used for neptunium.[k] In March 2016, Morita proposed the name "nihonium" to IUPAC, with the symbol Nh.[70] The naming realised what had been a national dream in Japanese science ever since Ogawa's claim.[63]

The former president of IUPAP, Cecilia Jarlskog, complained at the Nobel Symposium on Superheavy Elements in Bäckaskog Castle, Sweden, in June 2016 about the lack of openness involved in the process of approving new elements, and stated that she believed that the JWP's work was flawed and should be redone by a new JWP. A survey of physicists determined that many felt that the Lund–GSI 2016 criticisms of the JWP report were well-founded, but that the conclusions would hold up if the work was redone, and the new president, Bruce McKellar, ruled that the proposed names should be released in a joint IUPAP–IUPAC press release.[68] Thus, IUPAC and IUPAP publicised the proposal of nihonium that June,[79] and set a five-month term to collect comments, after which the name would be formally established at a conference.[82][83] The name was officially approved in November 2016.[84] The naming ceremony for the new element was held in Tokyo, Japan, in March 2017, with Naruhito, then the Crown Prince of Japan, in attendance.[85]

Isotopes[edit]

Main article: Isotopes of nihonium

Isotope Half-life[l]Decay
mode
Discovery
year[86]
Discovery
reaction[87]
Value Ref
278Nh 2.3 ms[86]α 2004 209Bi(70Zn,n)
282Nh 73 ms[88]α 2007 237Np(48Ca,3n)
283Nh 75 ms[88]α 2004 287Mc(—,α)
284Nh 0.91 s[88]α, EC 2004 288Mc(—,α)
285Nh 4.2 s[88]α 2010 289Mc(—,α)
286Nh 9.5 s[88]α 2010 290Mc(—,α)
287Nh[m]5.5 s[8]α 1999 287Fl(ee)
290Nh[m]2 s[9]α 1998 290Fl(ee)

Nihonium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesised in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Eight different isotopes of nihonium have been reported with atomic masses 278, 282–287, and 290 (287Nh and 290Nh are unconfirmed); they all decay through alpha decay to isotopes of roentgenium;[89] there have been indications that nihonium-284 can also decay by electron capture to copernicium-284.[90]

Stability and half-lives[edit]

A chart of heavy nuclides with their known and predicted half-lives (known nuclides shown with borders). Nihonium (row 113) is expected to be within the "island of stability" (white circle) and thus its nuclei are slightly more stable than would otherwise be predicted; the known nihonium isotopes are too neutron-poor to be within the island.

The stability of nuclei quickly decreases with the increase in atomic number after curium, element 96, whose half-life is over ten thousand times longer than that of any subsequent element. All isotopes with an atomic number above 101 undergo radioactive decay with half-lives of less than 30 hours: this is because of the ever-increasing Coulomb repulsion of protons, so that the strong nuclear force cannot hold the nucleus together against spontaneous fission for long. Calculations suggest that in the absence of other stabilising factors, elements with more than 103 protons should not exist. Researchers in the 1960s suggested that the closed nuclear shells around 114 protons and 184 neutrons should counteract this instability, and create an "island of stability" containing nuclides with half-lives reaching thousands or millions of years. The existence of the island is still unproven, but the existence of the superheavy elements (including nihonium) confirms that the stabilising effect is real, and in general the known superheavy nuclides become longer-lived as they approach the predicted location of the island.[91][92]

All nihonium isotopes are unstable and radioactive; the heavier nihonium isotopes are more stable than the lighter ones, as they are closer to the centre of the island. The most stable known nihonium isotope, 286Nh, is also the heaviest; it has a half-life of 8 seconds. The isotope 285Nh, as well as the unconfirmed 287Nh and 290Nh, have also been reported to have half-lives of over a second. The isotopes 284Nh and 283Nh have half-lives of 1 and 0.1 seconds respectively. The remaining two isotopes have half-lives between 0.1 and 100 milliseconds: 282Nh has a half-life of 70 milliseconds, and 278Nh, the lightest known nihonium isotope, is also the shortest-lived, with a half-life of 1.4 milliseconds. This rapid increase in the half-lives near the closed neutron shell at N = 184 is seen in roentgenium, copernicium, and nihonium (elements 111 through 113), where each extra neutron so far multiplies the half-life by a factor of 5 to 20.[92][93]

Predicted properties[edit]

Very few properties of nihonium or its compounds have been measured; this is due to its extremely limited and expensive production[16] and the fact it decays very quickly. Properties of nihonium mostly remain unknown and only predictions are available.

Physical and atomic[edit]

Atomic energy levels of outermost s, p, and d electrons of thallium and nihonium[94]

Nihonium is the first member of the 7p series of elements and the heaviest group 13 element on the periodic table, below boron, aluminium, gallium, indium, and thallium. All the group 13 elements except boron are metals, and nihonium is expected to follow suit. Nihonium is predicted to show many differences from its lighter homologues. The major reason for this is the spin–orbit (SO) interaction, which is especially strong for the superheavy elements, because their electrons move much faster than in lighter atoms, at velocities close to the speed of light.[5] In relation to nihonium atoms, it lowers the 7s and the 7p electron energy levels (stabilising those electrons), but two of the 7p electron energy levels are stabilised more than the other four.[95] The stabilisation of the 7s electrons is called the inert pair effect, and the separation of the 7p subshell into the more and less stabilised parts is called subshell splitting. Computational chemists see the split as a change of the second, azimuthal quantum numberl, from 1 to 1/2 and 3/2 for the more and less stabilised parts of the 7p subshell, respectively.[5][n] For theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s2 7p1/21.[1] The first ionisation energy of nihonium is expected to be 7.306 eV, the highest among the metals of group 13.[1] Similar subshell splitting should exist for the 6d electron levels, with four being 6d3/2 and six being 6d5/2. Both these levels are raised to be close in energy to the 7s ones, high enough to possibly be chemically active. This would allow for the possibility of exotic nihonium compounds without lighter group 13 analogues.[95]

Periodic trends would predict nihonium to have an atomic radius larger than that of thallium due to it being one period further down the periodic table, but calculations suggest nihonium has an atomic radius of about 170 pm, the same as that of thallium, due to the relativistic stabilisation and contraction of its 7s and 7p1/2 orbitals. Thus, nihonium is expected to be much denser than thallium, with a predicted density of about 16 to 18 g/cm3 compared to thallium's 11.85 g/cm3, since nihonium atoms are heavier than thallium atoms but have the same volume.[1][94] Bulk nihonium is expected to have a hexagonal close-packed crystal structure, like thallium.[6] The melting and boiling points of nihonium have been predicted to be 430 °C and 1100 °C respectively, exceeding the values for gallium, indium, and thallium, following periodic trends.[1][2] Nihonium should have a bulk modulus of 20.8 GPa, about half that of thallium (43 GPa).[7]

Chemical[edit]

The chemistry of nihonium is expected to be very different from that of thallium. This difference stems from the spin–orbit splitting of the 7p shell, which results in nihonium being between two relatively inert closed-shell elements (copernicium and flerovium), an unprecedented situation in the periodic table.[96] Nihonium is expected to be less reactive than thallium, because of the greater stabilisation and resultant chemical inactivity of the 7s subshell in nihonium compared to the 6s subshell in thallium.[4] The standard electrode potential for the Nh+/Nh couple is predicted to be 0.6 V. Nihonium should be a rather noble metal.[4]

The metallic group 13 elements are typically found in two oxidation states: +1 and +3. The former results from the involvement of only the single p electron in bonding, and the latter results in the involvement of all three valence electrons, two in the s-subshell and one in the p-subshell. Going down the group, bond energies decrease and the +3 state becomes less stable, as the energy released in forming two additional bonds and attaining the +3 state is not always enough to outweigh the energy needed to involve the s-electrons. Hence, for aluminium and gallium +3 is the most stable state, but +1 gains importance for indium and by thallium it becomes more stable than the +3 state. Nihonium is expected to continue this trend and have +1 as its most stable oxidation state.[1]

The simplest possible nihonium compound is the monohydride, NhH. The bonding is provided by the 7p1/2 electron of nihonium and the 1s electron of hydrogen. The SO interaction causes the binding energy of nihonium monohydride to be reduced by about 1 eV[1] and the nihonium–hydrogen bond length to decrease as the bonding 7p1/2 orbital is relativistically contracted. This is unique among the 7p element monohydrides; all the others have relativistic expansion of the bond length instead of contraction.[97] Another effect of the SO interaction is that the Nh–H bond is expected to have significant pi bonding character (side-on orbital overlap), unlike the almost pure sigma bonding (head-on orbital overlap) in thallium monohydride (TlH).[98] The analogous monofluoride (NhF) should also exist.[94] Nihonium(I) is predicted to be more similar to silver(I) than thallium(I):[1] the Nh+ ion is expected to more willingly bind anions, so that NhCl should be quite soluble in excess hydrochloric acid or ammonia; TlCl is not. In contrast to Tl+, which forms the strongly basic hydroxide (TlOH) in solution, the Nh+ cation should instead hydrolyse all the way to the amphoteric oxide Nh2O, which would be soluble in aqueous ammonia and weakly soluble in water.[4]

The adsorption behaviour of nihonium on gold surfaces in thermochromatographical experiments is expected to be closer to that of astatine than that of thallium. The destabilisation of the 7p3/2 subshell effectively leads to a valence shell closing at the 7s2 7p2 configuration rather than the expected 7s2 7p6 configuration with its stable octet. As such, nihonium, like astatine, can be considered to be one p-electron short of a closed valence shell. Hence, even though nihonium is in group 13, it has several properties similar to the group 17 elements. (Tennessine in group 17 has some group-13-like properties, as it has three valence electrons outside the 7s2 7p2 closed shell.[99]) Nihonium is expected to be able to gain an electron to attain this closed-shell configuration, forming the −1 oxidation state like the halogens (fluorine, chlorine, bromine, iodine, and astatine). This state should be more stable than it is for thallium as the SO splitting of the 7p subshell is greater than that for the 6p subshell.[5] Nihonium should be the most electronegative of the metallic group 13 elements,[1] even more electronegative than tennessine, the period 7 congener of the halogens: in the compound NhTs, the negative charge is expected to be on the nihonium atom rather than the tennessine atom.[94] The −1 oxidation should be more stable for nihonium than for tennessine.[1][100] The electron affinity of nihonium is calculated to be around 0.68 eV, higher than thallium's at 0.4 eV; tennessine's is expected to be 1.8 eV, the lowest in its group.[1] It is theoretically predicted that nihonium should have an enthalpy of sublimation around 150 kJ/mol and an enthalpy of adsorption on a gold surface around −159 kJ/mol.[101]

Skeletal model of a trigonal molecule with a central atom (boron) symmetrically bonded to three peripheral (chlorine) atoms

BCl
3 has a trigonal structure.

Skeletal model of a planar molecule with a central atom (iodine) symmetrically bonded to three (chlorine) atoms to form a big right-angled 2

NhCl
3 is predicted to be T-shaped.

Significant 6d involvement is expected in the Nh–Au bond, although it is expected to be more unstable than the Tl–Au bond and entirely due to magnetic interactions. This raises the possibility of some transition metal character for nihonium.[96] On the basis of the small energy gap between the 6d and 7s electrons, the higher oxidation states +3 and +5 have been suggested for nihonium.[1][4] Some simple compounds with nihonium in the +3 oxidation state would be the trihydride (NhH3), trifluoride (NhF3), and trichloride (NhCl3). These molecules are predicted to be T-shaped and not trigonal planar as their boron analogues are:[o] this is due to the influence of the 6d5/2 electrons on the bonding.[98][p] The heavier nihonium tribromide (NhBr3) and triiodide (NhI3) are trigonal planar due to the increased steric repulsion between the peripheral atoms; accordingly, they do not show significant 6d involvement in their bonding, though the large 7s–7p energy gap means that they show reduced sp2 hybridisation compared to their boron analogues.[98]

The bonding in the lighter NhX3 molecules can be considered as that of a linear NhX+
2 species (similar to HgF2 or AuF
2) with an additional Nh–X bond involving the 7p orbital of nihonium perpendicular to the other two ligands. These compounds are all expected to be highly unstable towards the loss of an X2 molecule and reduction to nihonium(I):[98]

NhX3 → NhX + X2

Nihonium thus continues the trend down group 13 of reduced stability of the +3 oxidation state, as all five of these compounds have lower reaction energies than the unknown thallium(III) iodide.[q] The +3 state is stabilised for thallium in anionic complexes such as TlI
4, and the presence of a possible vacant coordination site on the lighter T-shaped nihonium trihalides is expected to allow a similar stabilisation of NhF
4 and perhaps NhCl
4.[98]

The +5 oxidation state is unknown for all lighter group 13 elements: calculations predict that nihonium pentahydride (NhH5) and pentafluoride (NhF5) should have a square pyramidal molecular geometry, but also that both would be highly thermodynamically unstable to loss of an X2 molecule and reduction to nihonium(III). Despite its instability, the possible existence of nihonium pentafluoride is entirely due to relativistic effects allowing the 6d electrons to participate in the bonding. Again, some stabilisation is expected for anionic complexes, such as NhF
6. The structures of the nihonium trifluoride and pentafluoride molecules are the same as those for chlorine trifluoride and pentafluoride.[98]

Experimental chemistry[edit]

The chemical characteristics of nihonium have yet to be determined unambiguously.[101][106] The isotopes 284Nh, 285Nh, and 286Nh have half-lives long enough for chemical investigation.[101] From 2010 to 2012, some preliminary chemical experiments were performed at the JINR to determine the volatility of nihonium. The isotope 284Nh was investigated, made as the daughter of 288Mc produced in the 243Am+48Ca reaction. The nihonium atoms were synthesised in a recoil chamber and then carried along polytetrafluoroethylene (PTFE) capillaries at 70 °C by a carrier gas to the gold-covered detectors. About ten to twenty atoms of 284Nh were produced, but none of these atoms were registered by the detectors, suggesting either that nihonium was similar in volatility to the noble gases (and thus diffused away too quickly to be detected) or, more plausibly, that pure nihonium was not very volatile and thus could not efficiently pass through the PTFE capillaries.[101] Formation of the hydroxide NhOH should ease the transport, as nihonium hydroxide is expected to be more volatile than elemental nihonium, and this reaction could be facilitated by adding more water vapour into the carrier gas. It seems likely that this formation is not kinetically favoured, so the longer-lived isotopes 285Nh and 286Nh were considered more desirable for future experiments.[101][107]

A 2017 experiment at the JINR, producing 284Nh and 285Nh via the 243Am+48Ca reaction as the daughters of 288Mc and 289Mc, avoided this problem by removing the quartz surface, using only PTFE. No nihonium atoms were observed after chemical separation, implying an unexpectedly large retention of nihonium atoms on PTFE surfaces. This experimental result for the interaction limit of nihonium atoms with a PTFE surface (−ΔHPTFE
ads(Nh) > 45 kJ/mol) disagrees significantly with previous theory, which expected a lower value of 14.00 kJ/mol. This suggests that the nihonium species involved in the previous experiment was likely not elemental nihonium but rather nihonium hydroxide, and that high-temperature techniques such as vacuum chromatography would be necessary to further probe the behaviour of elemental nihonium.[108]Bromine saturated with boron tribromide has been suggested as a carrier gas for experiments on nihonium chemistry; this oxidises nihonium's lighter congener thallium to thallium(III), providing an avenue to investigate the oxidation states of nihonium, similar to earlier experiments done on the bromides of group 5 elements, including the superheavy dubnium.[109]

See also[edit]

Notes[edit]

  1. ^In nuclear physics, an element is called heavy if its atomic number is high; lead (element 82) is one example of such a heavy element. The term "superheavy elements" typically refers to elements with atomic number greater than 103 (although there are other definitions, such as atomic number greater than 100[11] or 112;[12] sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypothetical superactinide series).[13] Terms "heavy isotopes" (of a given element) and "heavy nuclei" mean what could be understood in the common language—isotopes of high mass (for the given element) and nuclei of high mass, respectively.
  2. ^In 2009, a team at JINR led by Oganessian published results of their attempt to create hassium in a symmetric 136Xe + 136Xe reaction. They failed to observe a single atom in such a reaction, putting the upper limit on the cross section, the measure of probability of a nuclear reaction, as 2.5 pb.[14] In comparison, the reaction that resulted in hassium discovery, 208Pb + 58Fe, had a cross section of ~20 pb (more specifically, 19+19
    −11 pb), as estimated by the discoverers.[15]
  3. ^The greater the excitation energy, the more neutrons are ejected. If the excitation energy is lower than energy binding each neutron to the rest of the nucleus, neutrons are not emitted; instead, the compound nucleus de-excites by emitting a gamma ray.[19]
  4. ^The definition by the IUPAC/IUPAP Joint Working Party states that a chemical element can only be recognized as discovered if a nucleus of it has not decayed within 10−14 seconds. This value was chosen as an estimate of how long it takes a nucleus to acquire its outer electrons and thus display its chemical properties.[20] This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.[21]
  5. ^This separation is based on that the resulting nuclei move past the target more slowly then the unreacted beam nuclei. The separator contains electric and magnetic fields whose effects on a moving particle cancel out for a specific velocity of a particle. Such separation can also be aided by a time-of-flight measurement and a recoil energy measurement; a combination of the two may allow to estimate the mass of a nucleus.
  6. ^Not all decay modes are caused by electrostatic repulsion. For example, beta decay is caused by the weak interaction.
  7. ^Since mass of a nucleus is not measured directly but is rather calculated from that of another nucleus, such measurement is called indirect. Direct measurements are also possible, but for the most part they have remained unavailable for heaviest nuclei.[30] The first direct measurement of mass of a superheavy nucleus was reported in 2018 at LBNL.[31] Mass was determined from the location of a nucleus after the transfer (the location helps determine its trajectory, which is linked to the mass-to-charge ratio of the nucleus, since the transfer was done in presence of a magnet).[32]
  8. ^Spontaneous fission was discovered by Soviet physicist Georgy Flerov,[33] a leading scientist at JINR, and thus it was a "hobbyhorse" for the facility.[34] In contrast, the LBL scientists believed fission information was not sufficient for a claim of synthesis of an element. They believed spontaneous fission had not been studied enough to use it for identification of a new element, since there was a difficulty of establishing that a compound nucleus had only ejected neutrons and not charged particles like protons or alpha particles.[21] They thus preferred to link new isotopes to the already known ones by successive alpha decays.[33]
  9. ^For instance, element 102 was mistakenly identified in 1957 at the Nobel Institute of Physics in Stockholm, Stockholm County, Sweden.[35] There were no earlier definitive claims of creation of this element, and the element was assigned a name by its Swedish, American, and British discoverers, nobelium. It was later shown that the identification was incorrect. The following year, LBNL was unable to reproduce the Swedish results and announced instead their synthesis of the element; that claim was also disproved later. JINR insisted that they were the first to create the element and suggested a name of their own for the new element, joliotium; the Soviet name was also not accepted (JINR later referred to the naming of element 102 as "hasty").[38] The name "nobelium" remained unchanged on account of its widespread usage.[39]
  10. ^Transactinide elements, such as nihonium, are produced by nuclear fusion. These fusion reactions can be divided into "hot" and "cold" fusion, depending on the excitation energy of the compound nucleus produced. "Cold fusion" in the context of superheavy element synthesis is a distinct concept from the idea that nuclear fusion can be achieved under room temperature conditions.[40] In hot fusion reactions, light, high-energy projectiles are accelerated towards heavy targets (actinides), creating compound nuclei at high excitation energy (~40–50 MeV) that may fission, or alternatively emit several (3 to 5) neutrons.[41] Cold fusion reactions use heavier projectiles, typically from the fourth period, and lighter targets, usually lead and bismuth. The fused nuclei produced have a relatively low excitation energy (~10–20 MeV), which decreases the probability that they will undergo fission reactions. As the fused nuclei cool to the ground state, they emit only one or two neutrons. Hot fusion produces more neutron-rich products because actinides have the highest neutron-to-proton ratios of any elements, and is currently the only method to produce the superheavy elements from flerovium (element 114) onwards.[42]
  11. ^Neptunium had been first reported at Riken by Nishina and Kenjiro Kimura in 1940, who did not get naming rights because they could not chemically separate and identify their discovery.[80][81]
  12. ^Different sources give different values for half-lives; the most recently published values are listed.
  13. ^ abThis isotope is unconfirmed
  14. ^The quantum number corresponds to the letter in the electron orbital name: 0 to s, 1 to p, 2 to d, etc.
  15. ^Among the stable group 13 elements, only boron forms monomeric halides at standard conditions; those of aluminium, gallium, indium, and thallium form ionic lattice structures or (in a few cases) dimerise.[102][103]
  16. ^The opposite effect is expected for the superheavy member of group 17, tennessine, due to the relativistic stabilisation of the 7p1/2 orbital: thus IF3 is T-shaped, but TsF3 is expected to be trigonal planar.[104]
  17. ^The compound with stoichiometry TlI3 is a thallium(I) compound involving the triiodide anion, I
    3.[105]

References[edit]

  1. ^ abcdefghijklmnopqrstHoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer Science+Business Media. ISBN .
  2. ^ abcSeaborg, Glenn T. (c. 2006). "transuranium element (chemical element)". Encyclopædia Britannica. Retrieved 16 March 2010.
  3. ^ abcBonchev, Danail; Kamenska, Verginia (1981). "Predicting the Properties of the 113–120 Transactinide Elements". Journal of Physical Chemistry. 85 (9): 1177–1186. doi:10.1021/j150609a021.
  4. ^ abcdefghijFricke, Burkhard (1975). "Superheavy elements: a prediction of their chemical and physical properties". Recent Impact of Physics on Inorganic Chemistry. Structure and Bonding. 21: 89–144. doi:10.1007/BFb0116498. ISBN . Retrieved 4 October 2013.
  5. ^ abcdThayer, John S. (2010). "Relativistic Effects and the Chemistry of the Heavier Main Group Elements". In Barysz, Maria; Ishikawa, Yasuyuki (eds.). Relativistic Methods for Chemists. Challenges and Advances in Computational Chemistry and Physics. 10. Springer. pp. 63–67. doi:10.1007/978-1-4020-9975-5_2. ISBN .
  6. ^ abKeller, O. L., Jr.; Burnett, J. L.; Carlson, T. A.; Nestor, C. W., Jr. (1969). "Predicted Properties of the Super Heavy Elements. I. Elements 113 and 114, Eka-Thallium and Eka-Lead". The Journal of Physical Chemistry. 74 (5): 1127−1134. doi:10.1021/j100700a029.
  7. ^ abAtarah, Samuel A.; Egblewogbe, Martin N. H.; Hagoss, Gebreyesus G. (2020). "First principle study of the structural and electronic properties of Nihonium". MRS Advances: 1–9. doi:10.1557/adv.2020.159.
Sours: https://en.wikipedia.org/wiki/Nihonium

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