The Element Neptunium
Atomic Number: 93
Atomic Weight: 237
Melting Point: 917 K (644°C or 1191°F)
Boiling Point: 4175 K (3902°C or 7056°F)
Density: 20.25 grams per cubic centimeter
Phase at Room Temperature: Solid
Element Classification: Metal
Period Number: 7
Group Number: none
Group Name: Actinide
Special Notes: Radioactive and Artificially Produced
What's in a name? Named for the planet Neptune.
Say what? Neptunium is pronounced as nep-TOO-nee-em.
History and Uses:
Neptunium was first produced by Edwin M. McMillian and Philip H. Abelson, working at the University of California, Berkeley, in 1940. They produced neptunium-239, an isotope of neptunium with a half-life of about 2.4 days, by bombarding uranium with slow moving neutrons.
Neptunium's most stable isotope, neptunium-237, has a half-life of about 2,144,000 years. It decays into protactinium-233 through alpha decay. Neptunium-237, which is produced in gram quantities as a by-product of the production of plutonium in nuclear reactors, is used in neutron detectors.
Once considered to be completely artificial, extremely small amounts of neptunium are produced naturally in uranium ores through the interaction of atoms of uranium in the ore with neutrons produced by the decay of other atoms of uranium in the ore.
Estimated Crustal Abundance: Not Applicable
Estimated Oceanic Abundance: Not Applicable
Number of Stable Isotopes: 0 (View all isotope data)
Ionization Energy: 6.266 eV
Oxidation States: +6, +5, +4, +3
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10 5f4
6s2 6p6 6d1