Atomic number:93

Group numbers:3

Period:7

Electronic configuration:[Rn] 5f⁴ 6d¹ 7s²

Formal oxidation number:+3 +4 +5 +6

Electronegativities:1.3

Atomic radius / pm:130

Relative atomic mass:[237]

 

Neptunium was discovered by Edwin Mattison McMillan and Philip Hauge Abelson (US) in 1940. Named after the planet Neptune. It is a rare, silvery radioactive, radiotoxic metal that resists alkalis, reacts with oxygen, acid and steam. Neptunium was produced by bombarding uranium with slow neutrons.

Density / g dm^-3:20250 (293 K)

Molar volume / cm³mol^-1:11.70 (293 K)

Electrical resistivity / μΩcm:122 (20 °C)

Thermal conductivity / W m^-1K^-1:6.3

Melting point / °C:644

Boiling point / °C:3902

Heat of fusion / kJ mol^-1:9.46

Heat of vaporization / kJ mol^-1:336.6

Heat of atomization / kJ mol^-1:457

1st ionization energy / kJ mol^-1:604.55

2nd ionization energy / kJ mol^-1:-

3rd ionization energy / kJ mol^-1:-

in the atmosphere / ppm:-

in the Earth's crust / ppm:-

in the oceans / ppm:-