Chemical Element: neptunium

(Modern Latin: named for the planet Neptune, the first planet beyond Uranus; radioactive metal)

Chemical-Element Information

Symbol: Np
Atomic number: 93
Year discovered: 1940

Discovered by: Edwin M. McMillan (born 1907), American physicist, and Philip Hauge Abelson (born 1913) at the University of California in Berkeley.


  • Neptunium was the first synthetic transuranium element of the actinide series.
  • It was discovered by McMillan and Abelson in 1940 at Berkeley, California.
  • They bombarded uranium with neutrons produced from a cyclotron.
  • The metal is about as malleable as uranium made under the same conditions.

Name in other languages:

French: neptunium

German: Neptunium

Italian: nettunio

Spanish: neptunio


Information about other elements may be seen at this Chemical Elements List.

A special unit about words that include chemo-, chem- may be seen here.