Fermium

Fermium is a synthetic radioactive element with atomic number 100. It is produced in nuclear reactions and named after physicist Enrico Fermi.

Atomic number: The number of protons in an atom’s nucleus, which determines its chemical element. Fermium has 100 protons, the defining feature that places it at element 100.
Ivy Mike: The United States’ first full-scale thermonuclear test, conducted at Enewetak Atoll in 1952. Its debris contained the first identified fermium, produced by intense neutron capture.
Neutron capture: A nuclear reaction in which an atomic nucleus absorbs a neutron. Repeated neutron capture helped create fermium in the intense neutron flux of Ivy Mike.
Actinide chemistry: The study of chemical behavior among the actinide elements. Fermium’s scarce atoms help test how chemical properties change across the actinide series.
Actinide: A series of metallic elements with atomic numbers 89 through 103, characterized by filling 5f orbitals. Fermium belongs to the actinide series, whose members are predominantly radioactive.
Albert Ghiorso: An American nuclear chemist who helped discover numerous transuranium elements. Ghiorso helped identify fermium in test debris and led work on its later production.
Beta decay: Radioactive decay in which a neutron changes into a proton, or a proton into a neutron, with emitted particles. Beta decay can raise a nucleus’s atomic number during the production of heavy elements.
Heavy-ion fusion: A nuclear reaction in which accelerated heavy nuclei collide and may combine. Heavy-ion reactions can synthesize fermium isotopes for nuclear-structure studies.
Isotope: One of two or more forms of an element whose atoms have different numbers of neutrons. Known fermium atoms differ chiefly by isotope, with different nuclear stability and lifetimes.
Lawrence Berkeley National Laboratory: A United States research laboratory founded in 1931 and known for nuclear and particle physics. Its teams developed methods to produce and identify fermium isotopes in the laboratory.

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Enrico FermiBroader topic: The element was named in Fermi’s honor after his death.