Neptunium
Properties
| Atomic Number | 93 |
| CAS Registry Number | 7439-99-8 |
| Chemical Symbol | Np |
History
The atomic number is 93 and the chemical symbol is Np. The name derives from the planet Neptune ( the Roman god of the sea) since it is the next outer-most planet beyond the planet uranus in the solar system and this element is the next one beyond uranium in the periodic table.It was first synthesized by Edwin M. McMillan and Philip H. Abelson in 1940 via the nuclear reaction 238U( n γ) 239U -> β --> 239Np. The longest half-life associated with this unstable element is 2.14 million year 237Np.Holden, Norman E., (2004). History of the origin of the chemical elements and their discoverers. National Nuclear Data Center. Retrieved from http://www.nndc.bnl.gov/content/elements.html