Fermium (Fm)
Actinide · Radioactive · Synthetic
Fermium, element 100, was found alongside einsteinium in hydrogen-bomb fallout. It is the heaviest element that can still be made in weighable (barely) quantities in nuclear reactors.
Position on the periodic table
Atomic properties
| Atomic number | 100 |
|---|---|
| Atomic mass | 257 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f12 |
| Noble gas shorthand | [Rn] 5f12 7s2 |
| Electrons per shell | 2, 8, 18, 32, 30, 8, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +3 |
| Electronegativity (Pauling) | 1.3 |
| Covalent radius (approx.) | Not available |
| First ionization energy | 627 kJ/mol |
| Electron affinity | 34 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | Not available |
| Melting point | 1526.8 °C (1800 K) |
| Boiling point | Not available |
| Appearance | Not available |
| Radioactive | Yes |
| Origin | Synthetic (lab-made) |
Electron configuration of fermium
Fermium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f12, usually shortened to [Rn] 5f12 7s2. Its electrons occupy 7 shells (2, 8, 18, 32, 30, 8, 2), placing it in period 7 of the f-block. Explore it interactively in the electron configuration calculator.
Uses of fermium
- Fundamental research only
Biological role: None.
Occurrence: Entirely synthetic.
History and discovery
Discovered: 1952 — Lawrence Berkeley National Laboratory. Name origin: Named after Enrico Fermi, architect of the first nuclear reactor.
Discovered in 1952 “Ivy Mike” fallout by Ghiorso's team; kept secret until 1955.
Safety notes
Radioactive research material only.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Fermium
1. What is the chemical symbol of Fermium?
2. What is the atomic number of Fermium?
3. Which category does Fermium belong to?
4. What is the state of Fermium at room temperature?
5. Which period of the periodic table is Fermium in?
Fermium FAQs
What is the atomic number of fermium?
Fermium's atomic number is 100 — every fermium atom has 100 protons in its nucleus.
What is the symbol for fermium?
Fm. Named after Enrico Fermi, architect of the first nuclear reactor.
Is fermium a metal, nonmetal, or metalloid?
Fermium is classified as a actinide.
What state is fermium at room temperature?
At about 25 °C, fermium is a solid. It melts at 1526.8 °C.
What is fermium used for?
Key uses include: fundamental research only.
Related elements
Keep working with this element
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