Množina: fermia

Synthesized, radioactive, metallic element of the actinide series, symbol Fm, atomic number 100, atomic weight 257. Ten isotopes are known, the longest-lived of which, Fm-257, has a half-life of 80 days. Fermium has been produced only in minute quantities in particle accelerators.
It was discovered in 1952 in the debris of the first thermonuclear explosion. The element was named 1955 in honor of US physicist Enrico Fermi.A radioactive transuranic metallic element produced by bombarding plutonium with neutrons; SYN. Fm, atomic number 100.