Fermium
actinideProperties
| Property | Value |
|---|---|
| Atomic Mass | 257 amu |
| Category | actinide |
| Period | 7 |
| Electron Configuration | [Rn] 5f12 7s2 |
| Electronegativity | 1.3 (Pauling) |
| Oxidation States | 3, 2 |
| Melting Point | 1800 K (1526.8 °C) |
| Discovered By | Albert Ghiorso, Glenn T. Seaborg (1952) |
About Fermium
Fermium first showed up in fallout from the 1952 Ivy Mike thermonuclear test, alongside einsteinium — both elements were synthesized accidentally when uranium-238 in the device captured a cascade of neutrons before anything fissioned. The discovery was classified for years. What makes fermium chemically interesting is also what makes it the end of a road: it sits at the boundary of what neutron capture can build. Fermium-258 fissions spontaneously with a half-life of about 0.37 milliseconds, so even in the highest-flux reactors, the chain that produced californium and einsteinium grinds to a halt at element 100. Everything heavier — mendelevium, nobelium, and the transactinides — has to be assembled atom by atom in a heavy-ion accelerator. The most stable isotope, Fm-257, has a 100.5-day half-life, and chemists have managed to study its solution behavior at tracer concentrations: Fm³⁺ behaves much like the late lanthanides, with the +2 state appearing in stronger reducing conditions than for its neighbors. No one has ever seen a weighable sample.
Fun Fact
Fermium marks the end of the road for making elements by neutron capture — fermium-258 fissions so rapidly that no amount of reactor neutron bombardment can push past element 100, creating a fundamental barrier in nuclear chemistry.
Common Uses
- Scientific research into actinide chemistry
- Nuclear physics experiments
- Studies of the limits of neutron-capture element synthesis
- Research into spontaneous fission barriers
- No commercial or practical applications