Neptunium

Neptunium (Np)

Radioactive metallic transuranic element, belongs to the actinoids. Np-237, the most stable isotope, has a half-life of 2.2*10^6 years and is a by product of nuclear reactors. The other known isotopes have mass numbers 229 through 236, and 238 through 241. Np-236 has a half-life of 5*10^3 years. First produced by Edwin M. McMillan and P.H. Abelson in 1940.
Atomic Number93
Atomic Weight237
Mass Number219
Group
Period7
Blockf
Protons93 p+
Neutrons126 n0
Electrons93 e-
Neptunium2.jpg Animated Bohr Model of Np (Neptunium) Enhanced Bohr Model of Np (Neptunium) Bohr Model: Np (Neptunium) Orbital Diagram of Np (Neptunium)

Properties

Atomic Radius
175 pm
Molar Volume
Covalent Radius
171 pm
Metallic Radius
Ionic Radius
110 pm
Crystal Radius
124 pm
Van der Waals Radius
239 pm
Density
20.2 g/cm³
Energy
Proton Affinity
Electron Affinity
Ionization Energy
Heat of Vaporization
336 kJ/mol
Heat of Fusion
9.6 kJ/mol
Heat of Formation
464.8 kJ/mol
Electrons
Electron Shells2, 8, 18, 32, 22, 9, 2
Valence Electrons6
Electron Configuration[Rn] 5f4 6d1 7s2
Oxidation States2, 3, 4, 5, 6, 7
Electronegativity
1.3
Electrophilicity
Phases
PhaseSolid
Gas Phase
Boiling Point
Melting Point
917.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color
Silver
Appearancesilvery metallic
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
Molar Heat Capacity
Specific Heat Capacity
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
TypeConductor
Electrical Conductivity
0.83 MS/m
Electrical Resistivity
0.0000012 m Ω
Superconducting Point
Magnetism
Type
Magnetic Susceptibility (Mass)
Magnetic Susceptibility (Molar)
Magnetic Susceptibility (Volume)
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal StructureSimple Orthorhombic (ORC)
Lattice Constant
4.72 Å
Lattice Anglesπ/2, π/2, π/2
Mechanical Properties
Hardness
Bulk Modulus
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
Classification
CategoryActinides, Actinides
CAS Group
IUPAC Group
Glawe Number37
Mendeleev Number22
Pettifor Number44
Geochemical Class
Goldschmidt Classsynthetic
Other
Gas Basicity
Dipole Polarizability
151 ± 20 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section
180
Neutron Mass Absorption
Quantum Numbers6L11/2
Space Group62 (Pnma)

Isotopes of Neptunium

Stable Isotopes0
Unstable Isotopes27
Radioactive Isotopes27

219Np

AbundanceRadioactive ☢️
Relative Atomic Mass
219.031601865 ± 0.000098732 Da
Mass Number219
G-Factor
Half Life
570 ± 450 us
Spin9/2
Quadrupole Moment
Discovery Year2015
Parity-

219Np Decay Modes
Decay ModeIntensity
α (α emission)100%

220Np

AbundanceRadioactive ☢️
Relative Atomic Mass
220.03271628 ± 0.000032977 Da
Mass Number220
G-Factor
Half Life
29 ± 11 ns
Spin1
Quadrupole Moment
Discovery Year2019
Parity-

220Np Decay Modes
Decay ModeIntensity
α (α emission)100%

221Np

AbundanceRadioactive ☢️
Relative Atomic Mass
221.03211 ± 0.000215 Da
Mass Number221
G-Factor
Half Life
Spin9/2
Quadrupole Moment
Discovery Year
Parity-

221Np Decay Modes
Decay ModeIntensity
α (α emission)%

222Np

AbundanceRadioactive ☢️
Relative Atomic Mass
222.033574706 ± 0.000040849 Da
Mass Number222
G-Factor
Half Life
480 ± 190 ns
Spin1
Quadrupole Moment
Discovery Year2020
Parity-

222Np Decay Modes
Decay ModeIntensity
α (α emission)100%

223Np

AbundanceRadioactive ☢️
Relative Atomic Mass
223.03291334 ± 0.000088956 Da
Mass Number223
G-Factor
Half Life
2.5 ± 0.8 us
Spin9/2
Quadrupole Moment
Discovery Year2017
Parity-

223Np Decay Modes
Decay ModeIntensity
α (α emission)100%

224Np

AbundanceRadioactive ☢️
Relative Atomic Mass
224.03438803 ± 0.000031052 Da
Mass Number224
G-Factor
Half Life
48 ± 19 us
Spin2
Quadrupole Moment
Discovery Year2018
Parity-

224Np Decay Modes
Decay ModeIntensity
α (α emission)100%

225Np

AbundanceRadioactive ☢️
Relative Atomic Mass
225.033943422 ± 0.000098355 Da
Mass Number225
G-Factor
Half Life
6.5 ± 3.5 ms
Spin9/2
Quadrupole Moment
Discovery Year1994
Parity-

225Np Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

226Np

AbundanceRadioactive ☢️
Relative Atomic Mass
226.035230364 ± 0.000109568 Da
Mass Number226
G-Factor
Half Life
35 ± 10 ms
Spin
Quadrupole Moment
Discovery Year1990
Parity

226Np Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

227Np

AbundanceRadioactive ☢️
Relative Atomic Mass
227.034975012 ± 0.000082651 Da
Mass Number227
G-Factor
Half Life
510 ± 60 ms
Spin5/2
Quadrupole Moment
Discovery Year1990
Parity+

227Np Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

228Np

AbundanceRadioactive ☢️
Relative Atomic Mass
228.036313 ± 0.000108 Da
Mass Number228
G-Factor
Half Life
61.4 ± 1.4 s
Spin4
Quadrupole Moment
Discovery Year1994
Parity+

228Np Decay Modes
Decay ModeIntensity
ϵ (electron capture)59%
α (α emission)41%
β+ SF (β+-delayed fission)0.012%

229Np

AbundanceRadioactive ☢️
Relative Atomic Mass
229.036287269 ± 0.000108618 Da
Mass Number229
G-Factor
Half Life
4 ± 0.18 m
Spin5/2
Quadrupole Moment
Discovery Year1968
Parity+

229Np Decay Modes
Decay ModeIntensity
α (α emission)68%
β+ (β+ decay; β+ = ϵ + e+)%

230Np

AbundanceRadioactive ☢️
Relative Atomic Mass
230.03782806 ± 0.000059051 Da
Mass Number230
G-Factor
Half Life
4.6 ± 0.3 m
Spin4
Quadrupole Moment
Discovery Year1968
Parity+

230Np Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)97%
α (α emission)3%

231Np

AbundanceRadioactive ☢️
Relative Atomic Mass
231.038243598 ± 0.000054916 Da
Mass Number231
G-Factor
Half Life
48.8 ± 0.2 m
Spin5/2
Quadrupole Moment
Discovery Year1950
Parity+

231Np Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)98%
α (α emission)2%

232Np

AbundanceRadioactive ☢️
Relative Atomic Mass
232.040107 ± 0.000107 Da
Mass Number232
G-Factor
Half Life
14.7 ± 0.3 m
Spin5
Quadrupole Moment
Discovery Year1950
Parity-

232Np Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
α (α emission)%

233Np

AbundanceRadioactive ☢️
Relative Atomic Mass
233.040739421 ± 0.000054729 Da
Mass Number233
G-Factor
Half Life
36.2 ± 0.1 m
Spin5/2
Quadrupole Moment
Discovery Year1950
Parity+

233Np Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
α (α emission)0.0007%

234Np

AbundanceRadioactive ☢️
Relative Atomic Mass
234.042893245 ± 0.000009014 Da
Mass Number234
G-Factor
0
Half Life
4.4 ± 0.1 d
Spin0
Quadrupole Moment
0
Discovery Year1949
Parity+

234Np Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

235Np

AbundanceRadioactive ☢️
Relative Atomic Mass
235.044061518 ± 0.00000149 Da
Mass Number235
G-Factor
Half Life
396.1 ± 1.2 d
Spin5/2
Quadrupole Moment
Discovery Year1949
Parity+

235Np Decay Modes
Decay ModeIntensity
ϵ (electron capture)99.9974%
α (α emission)0.0026%

236Np

AbundanceRadioactive ☢️
Relative Atomic Mass
236.046568296 ± 0.000054129 Da
Mass Number236
G-Factor
Half Life
153 ± 5 ky
Spin6
Quadrupole Moment
Discovery Year1949
Parity-

236Np Decay Modes
Decay ModeIntensity
ϵ (electron capture)86.3%
β (β decay)13.5%
α (α emission)0.16%

237Np

AbundanceRadioactive ☢️
Relative Atomic Mass
237.04817164 ± 0.000001201 Da
Mass Number237
G-Factor
Half Life
2.144 ± 0.007 My
Spin5/2
Quadrupole Moment
3.886 ± 0.006
Discovery Year1948
Parity+

237Np Decay Modes
Decay ModeIntensity
α (α emission)100%
SF (spontaneous fission)2%
30Mg4%

238Np

AbundanceRadioactive ☢️
Relative Atomic Mass
238.050944603 ± 0.00000122 Da
Mass Number238
G-Factor
Half Life
2.099 ± 0.002 d
Spin2
Quadrupole Moment
Discovery Year1949
Parity+

238Np Decay Modes
Decay ModeIntensity
β (β decay)100%

239Np

AbundanceRadioactive ☢️
Relative Atomic Mass
239.052937538 ± 0.000001406 Da
Mass Number239
G-Factor
Half Life
2.356 ± 0.003 d
Spin5/2
Quadrupole Moment
Discovery Year1940
Parity+

239Np Decay Modes
Decay ModeIntensity
β (β decay)100%
α (α emission)%

240Np

AbundanceRadioactive ☢️
Relative Atomic Mass
240.056163778 ± 0.000018284 Da
Mass Number240
G-Factor
Half Life
61.9 ± 0.2 m
Spin5
Quadrupole Moment
Discovery Year1953
Parity+

240Np Decay Modes
Decay ModeIntensity
β (β decay)100%

241Np

AbundanceRadioactive ☢️
Relative Atomic Mass
241.058309671 ± 0.00010736 Da
Mass Number241
G-Factor
Half Life
13.9 ± 0.2 m
Spin5/2
Quadrupole Moment
Discovery Year1959
Parity+

241Np Decay Modes
Decay ModeIntensity
β (β decay)100%
α (α emission)%

242Np

AbundanceRadioactive ☢️
Relative Atomic Mass
242.061639548 ± 0.000214712 Da
Mass Number242
G-Factor
Half Life
2.2 ± 0.2 m
Spin1
Quadrupole Moment
Discovery Year1979
Parity+

242Np Decay Modes
Decay ModeIntensity
β (β decay)100%

243Np

AbundanceRadioactive ☢️
Relative Atomic Mass
243.064204 ± 0.000034 Da
Mass Number243
G-Factor
Half Life
1.85 ± 0.15 m
Spin5/2
Quadrupole Moment
Discovery Year1979
Parity+

243Np Decay Modes
Decay ModeIntensity
β (β decay)100%

244Np

AbundanceRadioactive ☢️
Relative Atomic Mass
244.067891 ± 0.000107 Da
Mass Number244
G-Factor
Half Life
2.29 ± 0.16 m
Spin7
Quadrupole Moment
Discovery Year1987
Parity-

244Np Decay Modes
Decay ModeIntensity
β (β decay)100%

245Np

AbundanceRadioactive ☢️
Relative Atomic Mass
245.070693 ± 0.000215 Da
Mass Number245
G-Factor
Half Life
Spin5/2
Quadrupole Moment
Discovery Year
Parity+

245Np Decay Modes
Decay ModeIntensity
β (β decay)%

History

Neptunium was the first synthetic transuranium element of the actinide series to be discovered. Neptunium was first produced by Edwin McMillan and Philip H. Abelson in 1940 at Berkeley Radiation Laboratory of the University of California. The team produced the neptunium isotope 239Np by bombarding uranium with slow moving neutrons. Named after the planet Neptune

DiscoverersE.M. McMillan, P.H. Abelson
Discovery LocationUnited States
Discovery Year1940
Etymology (Name Origin)Named for the planet Neptune.
Pronunciationnep-TOO-ni-em (English)
Neptunium is harmful due to its radioactivity
Neptunium is obtained as a by-product from nuclear reactors

Uses

Neptunium is used mainly for research purposes. When bombarded with neutrons 237Np is used to produce 238Pu which is used for spacecraft generators and terrestrial navigation beacons. 237Np is used in devices for detecting high-energy neutrons. It has no significant commercial applications.

Sources

Produced by bombarding uranium with slow neutrons.

Abundance
Abundance in Earth's crust
Abundance in Oceans
Abundance in Human Body
0 %
Abundance in Meteor
0 %
Abundance in Sun
0 %
Abundance in Universe
0 %

Nuclear Screening Constants