Neptunium (symbol Np, atomic number 93) is the first transuranium element, a by-product of nuclear reactors. It is classified as a actinide and sits in the actinide series (f-block), period 7 of the periodic table.
Overview
Neptunium is the chemical element with atomic number 93 and the symbol Np. With a standard atomic weight of [237], it is a actinide. In the periodic table it occupies the actinide series (f-block) and period 7, and under standard conditions it is normally a solid. Neptunium is the first transuranium element, a by-product of nuclear reactors.
Atomic structure
An atom of Neptunium has 93 protons in its nucleus and, when neutral, 93 electrons arranged in the configuration [Rn] 5f4 6d1 7s2. Neptunium has no stable isotope; the value [237] refers to the mass number of its most stable or most commonly produced isotope.
Discovery and place in the table
Neptunium was discovered in 1940 by Edwin McMillan, Philip H. Abelson. It follows Uranium (U) and precedes Plutonium (Pu) in order of atomic number.
| Atomic number | 93 |
|---|---|
| Symbol | Np |
| Atomic mass | [237] |
| Category | Actinide |
| Group | — |
| Period | 7 |
| Electron configuration | [Rn] 5f4 6d1 7s2 |
| Phase at STP | Solid |
| Discovered | 1940 (Edwin McMillan, Philip H. Abelson) |