Element Fermium, Fm

Fermium, as well as Einsteinium, was discovered in the debris from the thermonuclear explosion in the Pacific Ocean in November 1952. Three groups of physicists and chemists in various American laboratories investigated hundreds of kilograms of explosion matter and separated hundreds of atoms of the elements 99 and element 100. Some of uranium-238 nuclei captured 17 neutrons creating ^{255U neutron-excess isotope which, after a chain of beta-decay reactions became Fermium-255. It was registered by the alpha-particles which fermium emits. Its half-life period is 20 hours.}