Discovery date : 1940
Discovered by: Edwin McMillan and Philip Abelson
Origin of the name: Neptunium was named after the planet Neptune.
Allotropes :
~>NEPTUNIUM s a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Neptunium metal is silvery and tarnishes when exposed to air. It is radioactive, poisonous, pyrophoric, and can accumulate in bones, which makes the handling of neptunium dangerous.
| FACT BOX | |||
| Group | Actinides | Melting point | 644°C, 1191°F, 917 K |
| Period | 7 | Boiling point | 3902°C, 7056°F, 4175 K |
| Block | f | Density (g cm−3) | 20.2 |
| Atomic number | 93 | Relative atomic mass | [237] |
| State at 20°C | Solid | Key isotopes | 237Np |
| Electron configuration | [Rn] 5f46d17s2 | CAS number | 7439-99-8 |
| ChemSpider ID | 22375 | ChemSpider is a free chemical structure database | |
In early 1934, Enrico Fermi in Italy tried to produce elements 93 and 94 by bombarding uranium with neutrons, and claimed success. Ida Tacke-Noddack questioned Fermi’s claim, pointing out he had failed to do a complete analysis, and all that he had found were fission products of uranium. (Fermi had in fact discovered nuclear fission but not realised it.) In 1938, Horia Hulubei and Yvette Cauchois claimed to have discovered element 93, but the claim was also criticised on the grounds that element 93 did not occur naturally.
Neptunium was first made in 1940 by Edwin McMillan and Philip Abelson at Berkeley, California. It came from a uranium target that had been bombarded with slow neutrons and which then emitted unusual beta-rays indicating a new isotope. Abelson proved there was indeed a new element present.