Fermium (symbol Fm, atomic number 100) is a synthetic actinide, the heaviest element that can be made by neutron bombardment. It is classified as a actinide and sits in the actinide series (f-block), period 7 of the periodic table.
Overview
Fermium is the chemical element with atomic number 100 and the symbol Fm. With a standard atomic weight of [257], 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. Fermium is a synthetic actinide, the heaviest element that can be made by neutron bombardment.
Atomic structure
An atom of Fermium has 100 protons in its nucleus and, when neutral, 100 electrons arranged in the configuration [Rn] 5f12 7s2. Fermium has no stable isotope; the value [257] refers to the mass number of its most stable or most commonly produced isotope.
Discovery and place in the table
Fermium was discovered in 1952 by Lawrence Berkeley National Laboratory. It follows Einsteinium (Es) and precedes Mendelevium (Md) in order of atomic number.
| Atomic number | 100 |
|---|---|
| Symbol | Fm |
| Atomic mass | [257] |
| Category | Actinide |
| Group | — |
| Period | 7 |
| Electron configuration | [Rn] 5f12 7s2 |
| Phase at STP | Solid |
| Discovered | 1952 (Lawrence Berkeley National Laboratory) |