neptunium

Symbol: Np
Atomic number: 93
Atomic weight: 237 (isotope with the longest known half-life)
Density (at room temperature and pressure): 20.45 g/cc
Melting point: 640°C
Boiling point: 3,902°C
Ground state electron configuration: [Rn]5f⁴6d¹7s²

Previous Uranium---Plutonium Next
To the Periodic Table

Nep*tu"ni*um (?), n. [NL.]

A new metallic element, of doubtful genuineness and uncertain indentification, said to exist in certain minerals, as columbite.

Hermann.

© Webster 1913.