Quick answerFermium (Fm) is an actinide with atomic number 100 and a mass number of 257 (the most stable isotope), in period 7. It was discovered by Albert Ghiorso and colleagues in 1952. It is used for actinide research and synthesising heavier elements. Its electron configuration is [Rn] 5f12 7s2.
Fermium is a synthetic actinide found in the fallout of the first hydrogen bomb, made only atom by atom since.
Key facts
| Symbol | Fm |
|---|---|
| Atomic number | 100 |
| Atomic mass | [257] — mass number of the most stable isotope |
| Category | actinide |
| Group | — (f-block element, no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f12 7s2 |
| Discovered | Albert Ghiorso and colleagues, 1952 |
| Uses | actinide research, synthesising heavier elements, nuclear studies |
Quick quiz
Three questions from the facts on this page. No sign-up, no score is saved.
Keep exploring
- Periodic table — all 118 elements
- Neptunium (Np) — another actinide, atomic number 93
- Plutonium (Pu) — another actinide, atomic number 94
- Americium (Am) — another actinide, atomic number 95
- Curium (Cm) — another actinide, atomic number 96
- Berkelium (Bk) — another actinide, atomic number 97
- Californium (Cf) — another actinide, atomic number 98
- Einsteinium (Es) — another actinide, atomic number 99
- Mendelevium (Md) — another actinide, atomic number 101
- Nobelium (No) — another actinide, atomic number 102
- Lawrencium (Lr) — another actinide, atomic number 103
- All actinide elements — on the periodic table
Sources & last updated
- CIAAW — Standard Atomic Weights
- PubChem Periodic Table
- Wikipedia — Timeline of chemical element discoveries
Last updated: . Figures are shown with their year; where sources disagree, the value is left out rather than estimated.