Neptunium (Np)

Neptunium is the 93rd element in the periodic table and has a symbol of Np and atomic number of 93. It has an atomic weight of (237) and a mass number of 219. Neptunium has ninety-three protons and one hundred twenty-six neutrons in its nucleus, and ninety-three electrons in seven shells. It is located in group zero, period seven and block f of the periodic table. 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 Number	93
Atomic Weight	237
Mass Number	219

Group
Period	7
Block	f

Protons	93 p⁺
Neutrons	126 n⁰
Electrons	93 e^-

Properties

Physical Properties
Atomic Radius	175 pm 281 pm
Molar Volume	21.1 cm³/mol
Covalent Radius	171 pm 136 pm 116 pm 190 pm
Metallic Radius
Ionic Radius	110 pm 101 pm 87 pm 98 pm 75 pm 72 pm 71 pm 117.8 pm
Crystal Radius	124 pm 115 pm 101 pm 112 pm 89 pm 86 pm 85 pm 131.8 pm
Van der Waals Radius	239 pm 252 pm 342.4 pm
Density	20.2 g/cm³
Energy
Proton Affinity
Electron Affinity
Ionization Energy	6.2655 eV/particle 11.5 eV/particle 19.7 eV/particle 33.8 eV/particle 48 eV/particle 65 eV/particle 92 eV/particle 107 eV/particle 121 eV/particle 136 eV/particle 151 eV/particle 179 eV/particle 196 eV/particle 233 eV/particle 252 eV/particle 355 eV/particle 382 eV/particle 408 eV/particle 438 eV/particle 466 eV/particle 495 eV/particle 535 eV/particle 565 eV/particle 596 eV/particle 626 eV/particle 770 eV/particle 810 eV/particle 850 eV/particle 880 eV/particle 980 eV/particle 1,020 eV/particle 1,130 eV/particle 1,170 eV/particle 1,280 eV/particle 1,360 eV/particle 1,430 eV/particle 1,510 eV/particle 1,590 eV/particle 1,670 eV/particle 1,740 eV/particle 1,820 eV/particle 1,910 eV/particle 1,990 eV/particle 2,070 eV/particle 2,140 eV/particle 2,200 eV/particle 2,310 eV/particle 2,675 eV/particle 2,745 eV/particle 2,817 eV/particle 2,894 eV/particle 2,969 eV/particle 3,041 eV/particle 3,181 eV/particle 3,255 eV/particle 3,338 eV/particle 3,413 eV/particle 3,718 eV/particle 3,792 eV/particle 3,872 eV/particle 3,947 eV/particle 4,353 eV/particle 4,441 eV/particle 4,658 eV/particle 4,744 eV/particle 7,610 eV/particle 7,770 eV/particle 7,950 eV/particle 8,130 eV/particle 8,310 eV/particle 8,480 eV/particle 8,890 eV/particle 9,070 eV/particle 9,270 eV/particle 9,450 eV/particle 9,970 eV/particle 10,130 eV/particle 10,300 eV/particle 10,460 eV/particle 11,740 eV/particle 11,930 eV/particle 12,320 eV/particle 12,500 eV/particle 25,870 eV/particle 26,300 eV/particle 26,770 eV/particle 27,210 eV/particle 31,910 eV/particle 32,500 eV/particle 33,300 eV/particle 33,722.2 eV/particle 132,901.8 eV/particle 135,202 eV/particle

Heat of Vaporization	336 kJ/mol
Heat of Fusion	9.6 kJ/mol
Heat of Formation	464.8 kJ/mol
Electrons
Electron Shells	2, 8, 18, 32, 22, 9, 2

Valence Electrons	2

Electron Configuration	[Rn] 5f⁴ 6d¹ 7s²

Oxidation States	2, 3, 4, 5, 6, 7
Electronegativity	0.14265 1.3
Electrophilicity
Phases
Phase	Solid
Gas Phase
Boiling Point
Melting Point	917.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Neptunium is a Silver. Np has a CPK of #ffffff, Jmol of #0080ff, and MOLCAS GV of #0080ff. The Appearance of Element 93 is silvery metallic.
Color	Silver #ffffff #0080ff #0080ff
Appearance	silvery metallic
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
Molar Heat Capacity
Specific Heat Capacity
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type	Conductor
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
The Crystal Structure of Neptunium is ORC. The lattice constant of Np is 4.72 Å. The lattice angles of Element 93 are π/2, π/2, π/2.
Crystal Structure	Simple Orthorhombic (ORC)
Lattice Constant	4.72 Å
Lattice Angles	π/2, π/2, π/2
Mechanical Properties

Hardness
Bulk Modulus
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
Classification
The Glawe Number of Neptunium is 37. The Mendeleev Number of Np is 22. The Pettifor Number of Element 93 is 44. The Goldschmidt Class of Neptunium (Np) is synthetic.
Category	Actinides, Actinides
CAS Group
IUPAC Group
Glawe Number	37
Mendeleev Number	22
Pettifor Number	44
Geochemical Class
Goldschmidt Class	synthetic
Other
The Dipole Polarizability of Neptunium is 151 plus or minus 20 a₀. The Allotropes of Np is . The Neutron Cross Section of Element 93 is 180. The Quantum Numbers of Neptunium (Np) is 6L11/2. The Space Group of Neptunium is 62 (Pnma).
Gas Basicity
Dipole Polarizability	151 ± 20 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section	180
Neutron Mass Absorption
Quantum Numbers	6L11/2
Space Group	62 (Pnma)

Isotopes of Neptunium

Stable Isotopes	0
Unstable Isotopes	27
Radioactive Isotopes	27

²¹⁹Np

Abundance	Radioactive ☢️
Relative Atomic Mass	219.031601865 ± 0.000098732 Da
Mass Number	219
G-Factor
Half Life	570 ± 450 us
Spin	9/2
Quadrupole Moment
Discovery Year	2015
Parity	-

²¹⁹Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²⁰Np

Abundance	Radioactive ☢️
Relative Atomic Mass	220.03271628 ± 0.000032977 Da
Mass Number	220
G-Factor
Half Life	29 ± 11 ns
Spin	1
Quadrupole Moment
Discovery Year	2019
Parity	-

²²⁰Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²¹Np

Abundance	Radioactive ☢️
Relative Atomic Mass	221.03211 ± 0.000215 Da
Mass Number	221
G-Factor
Half Life
Spin	9/2
Quadrupole Moment
Discovery Year
Parity	-

²²¹Np Decay Modes

Decay Mode	Intensity
α (α emission)	%

²²²Np

Abundance	Radioactive ☢️
Relative Atomic Mass	222.033574706 ± 0.000040849 Da
Mass Number	222
G-Factor
Half Life	480 ± 190 ns
Spin	1
Quadrupole Moment
Discovery Year	2020
Parity	-

²²²Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²³Np

Abundance	Radioactive ☢️
Relative Atomic Mass	223.03291334 ± 0.000088956 Da
Mass Number	223
G-Factor
Half Life	2.5 ± 0.8 us
Spin	9/2
Quadrupole Moment
Discovery Year	2017
Parity	-

²²³Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²⁴Np

Abundance	Radioactive ☢️
Relative Atomic Mass	224.03438803 ± 0.000031052 Da
Mass Number	224
G-Factor
Half Life	48 ± 19 us
Spin	2
Quadrupole Moment
Discovery Year	2018
Parity	-

²²⁴Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²⁵Np

Abundance	Radioactive ☢️
Relative Atomic Mass	225.033943422 ± 0.000098355 Da
Mass Number	225
G-Factor
Half Life	6.5 ± 3.5 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1994
Parity	-

²²⁵Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²²⁶Np

Abundance	Radioactive ☢️
Relative Atomic Mass	226.035230364 ± 0.000109568 Da
Mass Number	226
G-Factor
Half Life	35 ± 10 ms
Spin
Quadrupole Moment
Discovery Year	1990
Parity

²²⁶Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²²⁷Np

Abundance	Radioactive ☢️
Relative Atomic Mass	227.034975012 ± 0.000082651 Da
Mass Number	227
G-Factor
Half Life	510 ± 60 ms
Spin	5/2
Quadrupole Moment
Discovery Year	1990
Parity	+

²²⁷Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²²⁸Np

Abundance	Radioactive ☢️
Relative Atomic Mass	228.036313 ± 0.000108 Da
Mass Number	228
G-Factor
Half Life	61.4 ± 1.4 s
Spin	4
Quadrupole Moment
Discovery Year	1994
Parity	+

²²⁸Np Decay Modes

Decay Mode	Intensity
ϵ (electron capture)	59%
α (α emission)	41%
β⁺ SF (β⁺-delayed fission)	0.012%

²²⁹Np

Abundance	Radioactive ☢️
Relative Atomic Mass	229.036287269 ± 0.000108618 Da
Mass Number	229
G-Factor
Half Life	4 ± 0.18 m
Spin	5/2
Quadrupole Moment
Discovery Year	1968
Parity	+

²²⁹Np Decay Modes

Decay Mode	Intensity
α (α emission)	68%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²³⁰Np

Abundance	Radioactive ☢️
Relative Atomic Mass	230.03782806 ± 0.000059051 Da
Mass Number	230
G-Factor
Half Life	4.6 ± 0.3 m
Spin	4
Quadrupole Moment
Discovery Year	1968
Parity	+

²³⁰Np Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	97%
α (α emission)	3%

²³¹Np

Abundance	Radioactive ☢️
Relative Atomic Mass	231.038243598 ± 0.000054916 Da
Mass Number	231
G-Factor
Half Life	48.8 ± 0.2 m
Spin	5/2
Quadrupole Moment
Discovery Year	1950
Parity	+

²³¹Np Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	98%
α (α emission)	2%

²³²Np

Abundance	Radioactive ☢️
Relative Atomic Mass	232.040107 ± 0.000107 Da
Mass Number	232
G-Factor
Half Life	14.7 ± 0.3 m
Spin	5
Quadrupole Moment
Discovery Year	1950
Parity	-

²³²Np Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	%

²³³Np

Abundance	Radioactive ☢️
Relative Atomic Mass	233.040739421 ± 0.000054729 Da
Mass Number	233
G-Factor
Half Life	36.2 ± 0.1 m
Spin	5/2
Quadrupole Moment
Discovery Year	1950
Parity	+

²³³Np Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	0.0007%

²³⁴Np

Abundance	Radioactive ☢️
Relative Atomic Mass	234.042893245 ± 0.000009014 Da
Mass Number	234
G-Factor	0
Half Life	4.4 ± 0.1 d
Spin	0
Quadrupole Moment	0
Discovery Year	1949
Parity	+

²³⁴Np Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

²³⁵Np

Abundance	Radioactive ☢️
Relative Atomic Mass	235.044061518 ± 0.00000149 Da
Mass Number	235
G-Factor
Half Life	396.1 ± 1.2 d
Spin	5/2
Quadrupole Moment
Discovery Year	1949
Parity	+

²³⁵Np Decay Modes

Decay Mode	Intensity
ϵ (electron capture)	99.9974%
α (α emission)	0.0026%

²³⁶Np

Abundance	Radioactive ☢️
Relative Atomic Mass	236.046568296 ± 0.000054129 Da
Mass Number	236
G-Factor
Half Life	153 ± 5 ky
Spin	6
Quadrupole Moment
Discovery Year	1949
Parity	-

²³⁶Np Decay Modes

Decay Mode	Intensity
ϵ (electron capture)	86.3%
β⁻ (β⁻ decay)	13.5%
α (α emission)	0.16%

²³⁷Np

Abundance	Radioactive ☢️
Relative Atomic Mass	237.04817164 ± 0.000001201 Da
Mass Number	237
G-Factor
Half Life	2.144 ± 0.007 My
Spin	5/2
Quadrupole Moment	3.886 ± 0.006
Discovery Year	1948
Parity	+

²³⁷Np Decay Modes

Decay Mode	Intensity
α (α emission)	100%
SF (spontaneous fission)	2%
30Mg	4%

²³⁸Np

Abundance	Radioactive ☢️
Relative Atomic Mass	238.050944603 ± 0.00000122 Da
Mass Number	238
G-Factor
Half Life	2.099 ± 0.002 d
Spin	2
Quadrupole Moment
Discovery Year	1949
Parity	+

²³⁸Np Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁹Np

Abundance	Radioactive ☢️
Relative Atomic Mass	239.052937538 ± 0.000001406 Da
Mass Number	239
G-Factor
Half Life	2.356 ± 0.003 d
Spin	5/2
Quadrupole Moment
Discovery Year	1940
Parity	+

²³⁹Np Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
α (α emission)	%

²⁴⁰Np

Abundance	Radioactive ☢️
Relative Atomic Mass	240.056163778 ± 0.000018284 Da
Mass Number	240
G-Factor
Half Life	61.9 ± 0.2 m
Spin	5
Quadrupole Moment
Discovery Year	1953
Parity	+

²⁴⁰Np Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴¹Np

Abundance	Radioactive ☢️
Relative Atomic Mass	241.058309671 ± 0.00010736 Da
Mass Number	241
G-Factor
Half Life	13.9 ± 0.2 m
Spin	5/2
Quadrupole Moment
Discovery Year	1959
Parity	+

²⁴¹Np Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
α (α emission)	%

²⁴²Np

Abundance	Radioactive ☢️
Relative Atomic Mass	242.061639548 ± 0.000214712 Da
Mass Number	242
G-Factor
Half Life	2.2 ± 0.2 m
Spin	1
Quadrupole Moment
Discovery Year	1979
Parity	+

²⁴²Np Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴³Np

Abundance	Radioactive ☢️
Relative Atomic Mass	243.064204 ± 0.000034 Da
Mass Number	243
G-Factor
Half Life	1.85 ± 0.15 m
Spin	5/2
Quadrupole Moment
Discovery Year	1979
Parity	+

²⁴³Np Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴⁴Np

Abundance	Radioactive ☢️
Relative Atomic Mass	244.067891 ± 0.000107 Da
Mass Number	244
G-Factor
Half Life	2.29 ± 0.16 m
Spin	7
Quadrupole Moment
Discovery Year	1987
Parity	-

²⁴⁴Np Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴⁵Np

Abundance	Radioactive ☢️
Relative Atomic Mass	245.070693 ± 0.000215 Da
Mass Number	245
G-Factor
Half Life
Spin	5/2
Quadrupole Moment
Discovery Year
Parity	+

²⁴⁵Np Decay Modes

Decay Mode	Intensity
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

Discoverers	E.M. McMillan, P.H. Abelson
Discovery Location	United States
Discovery Year	1940
Etymology (Name Origin)	Named for the planet Neptune.
Pronunciation	nep-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

Neptunium on ChemicalAid

Australian Educational Vocabulary ID	scot/3547
CAB ID	7537
CAS Registry Number	7439-99-8
ChEBI ID	33387
ChemSpider ID	22375
DSSTOX compound identifier	DTXCID3047639
DSSTox substance ID	DTXSID5074840
Den Store Danske ID	neptunium
ECHA Substance Infocard ID	100.028.280
Elhuyar ZTH ID	028601
Encyclopædia Britannica Online ID	science/neptunium
Encyclopædia Universalis ID	neptunium
Freebase ID	/m/025s4ry
French Vikidia ID	Neptunium
GND ID	4171471-4
Great Russian Encyclopedia Online ID	2262013
InChI	InChI=1S/Np
InChIKey	LFNLGNPSGWYGGD-UHFFFAOYSA-N
KBpedia ID	Neptunium
Library of Congress authority ID	sh85090879
MeSH descriptor ID	D009405
Namuwiki ID	넵투늄
National Library of Israel J9U ID	987007565628105171
OmegaWiki Defined Meaning	377199
OpenAlex ID	C516372188
PubChem CID	23933
Quora topic ID	Neptunium
Römpp online ID	RD-14-00817
Store norske leksikon ID	neptunium
Treccani ID	nettunio
UNII	6200K977BQ
USGS Thesaurus ID	1518
WordNet 3.1 Synset ID	14670581-n
YSO ID	12863

Neptunium (Np)

Properties

Isotopes of Neptunium

219Np

219Np Decay Modes

220Np

220Np Decay Modes

221Np

221Np Decay Modes

222Np

222Np Decay Modes

223Np

223Np Decay Modes

224Np

224Np Decay Modes

225Np

225Np Decay Modes

226Np

226Np Decay Modes

227Np

227Np Decay Modes

228Np

228Np Decay Modes

229Np

229Np Decay Modes

230Np

230Np Decay Modes

231Np

231Np Decay Modes

232Np

232Np Decay Modes

233Np

233Np Decay Modes

234Np

234Np Decay Modes

235Np

235Np Decay Modes

236Np

236Np Decay Modes

237Np

237Np Decay Modes

238Np

238Np Decay Modes

239Np

239Np Decay Modes

240Np

240Np Decay Modes

241Np

241Np Decay Modes

242Np

242Np Decay Modes

243Np

243Np Decay Modes

244Np

244Np Decay Modes

245Np

245Np Decay Modes