Symbol	Np
Atomic number	93
Group	-
Period	7
Block	f
Classification	Actinide

Appearance	Silvery metallic
Color	Silver

Number of protons	93 p+
Number of neutrons	144 n0
Number of electrons	93 e-

From Wikipedia, the free encyclopediaNeptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus.

Phase at STP	Solid
Density	20.45 g/cm3
Atomic weight	237 u

Melting point	912 K 638.85 °C 1181.93 °F
Boiling point	4447 K 4173.85 °C 7544.93 °F
Heat of vaporization	336 kJ/mol

Electronegativity (Pauling Scale)	1.36
Electron affinity	45.85 kJ/mol
Oxidation states	+2, +3, +4, +5, +6, +7 (an amphoteric oxide)
Ionization energies	604.5 kJ/mol 1128 kJ/mol 1997 kJ/mol 3242 kJ/mol

Electron configuration Shorthand configuration	[Rn] 5f4 6d1 7s2
Electron configuration Full configuration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f4 6s2 6p6 6d1 7s2
Electron configuration chart	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f4 6s2 6p6 6d1 7s2
Electrons per shell	2, 8, 18, 32, 22, 9, 2
Valence electrons	2
Valency electrons	6
Bohr model	Figure: Shell diagram of Neptunium (Np) atom.
Orbital Diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s

Discovery

Edwin McMillan, Philip H. Abelson (1940)

CAS Number	7439-99-8
ChemSpider ID	22375
EC number	231-108-8
PubChem CID Number	23933