Neptunium

Atomic number

93

Atomic mass (u)

237.048172

Category

Actinide

Standard state

Solid

Melting point

643.85 °C (917 K)

Boiling point

3901.85 °C (4175 K)

Density (g/cm³)

20.25

Electronegativity (Pauling)

1.36

Electron configuration

[Rn]7s2 5f4 6d1

Oxidation states

+6, +5, +4, +3

Atomic radius (pm)

221

First ionization energy (eV)

6.266

Discovery & recognition

Discovery year / period (PubChem)

1940

Discovery credited to (RSC)

Edwin McMillan and Philip Abelson

Date or period recorded by RSC

1940

Discovery place

Berkeley, California, United States

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

This transuranium element is primarily produced through nuclear reactions in reactors or particle accelerators. Some transuranium elements also occur naturally in extremely small traces; that is different from a mineable deposit.

“Neptunium is obtained as a by-product from nuclear reactors.”

Royal Society of Chemistry · occurrence excerpt ↗

Continue the research

Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.