Neptunium

Chemical, physical and material properties and data of the chemical element Neptunium.

Contents

General Information about Neptunium

Regular nameNeptuniumChemical symbolNpOther namesHistorical namesName meaning, originDiscovery (year)OccurencePosition in the PSEGroup membership

Atomar Properties of Neptunium

Atomic number Z93 = number of protonsStandard Atomic Weight237.048174914

Electron configuration of Neptunium

1s	2s	2p	3s	3p	3d	4s	4p	4d	4f	5s	5p	5d	5f	6s	6p	6d	6f	7s	7p
2	2	6	2	6	10	2	6	10	14	2	6	10	4	2	6	1		2

Shorthand electron configuration of Neptunium: [Rn] 5f⁴ 6d¹ 7s² .

Ionization Energies of Neptunium

The following table lists the ionization energies IE (ionization potentials); the IE is the energy required in electron volt (eV) per atom to separate a given electron from an Neptunium atom.

IE1
6.2657

Isotopic Data of Neptunium

An overview of the nuclides as well as the isotopic data and properties are listed on the following page: Neptunium isotopes.

Chemistry of Neptunium

Oxidation states+ 5Electronegativity1.3 (Pauling original)
1.36 (Pauling)Electron affinity0.48 eV
45.85 kJ mol^-1

Standard Electrode Potential

E⁰ (V)	Symbol	N_ox	Name Ox. Name Red.	Ox. Red.	e^-
-1.856	Np	+ III 0	Neptunium(III) cation Neptunium	Np³⁺ ⇄ Np (s)	+ 3 e^-
-0.962	Np	+ IV + III	Neptunium(IV) oxide Neptunium(III) hydroxide	NpO₂ + H₂O + H⁺ ⇄ Np(OH)₃	+ e^-
0.147	Np	+ IV + III	Neptunium(IV) cation Neptunium(III) cation	Np⁴⁺ ⇄ Np³⁺	+ e^-

Material and Physical Properties

Melting point644 °CEnthalpy of fusion (molar)3.20 kJ mol^-1Boiling point3902 °CEnthalpy of vaporization336.6 kJ mol^-1Density20.2 g cm^-3

External Data, Identifiers

CAS registry number7439-99-8InChI =1S/NpInChIKeyLFNLGNPSGWYGGD-UHFFFAOYSA-NPubChem ID23933

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Last update: 2022-12-12

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