Neptunium was discovered by Edwin M. McMillan and Philip H. Abelson in 1940 at Berkeley, California, USA.
Name: Neptunium
Symbol: Np
Atomic number: 93
Atomic weight: 237.05
State: solid
Group, period, block: n/a, 7, f
Color: silvery metallic
Classification: actinide
Electron configuration: 5f4 6d1 7s2
2,8,18,32,22,9,2
Physical properties
Density: 520.45[1] g/cm-3
Melting point: 910 K,637 °C,1179 °F
Boiling point: 4273 K,4000 °C,7232 °F
Atomic properties
Oxidation states: 7, 6, 5, 4, 3
Electronegativity: 1.36 (Pauling scale)
Ionization energies: 1st: 604.5 kJ·mol-1
Covalent radius: 190±1 pm
Van der Waals radius: no data
- Np
Electron Configuration
Isotopes
Neptunium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The isotope first synthesized was 239Np in 1940.