Fermium << FUR mee uhm >> is an artificially created radioactive element. Its chemical symbol is Fm, and its atomic number (number of protons in its nucleus) is 100.
Chemists place fermium in the actinide group of transuranium elements. For information on the position of fermium on the periodic table, see the article Periodic table.
Fermium has more than a dozen known isotopes, forms with the same number of protons but different numbers of neutrons. The most stable isotope has an atomic mass number (total number of protons and neutrons) of 257. That isotope has a half-life of 100.5 days—that is, due to radioactive decay, only half the atoms in a sample of isotope 257 would still be atoms of that isotope after 100.5 days. A team of American scientists led by Albert Ghiorso discovered fermium in 1953. They found it in radioactive debris produced by the first hydrogen bomb explosion in 1952. Fermium was named for Enrico Fermi, the Italian-born nuclear physicist who produced the first controlled nuclear chain reaction (see Fermi, Enrico).
Extremely small amounts of fermium are produced in nuclear reactors for scientific research. Chemical compounds of fermium have not been produced in weighable amounts. Therefore, its chemical properties are not completely known to scientists.
See also Einsteinium.
