The element 101 was synthesized for the first time, in 1955, in the Laboratory of Radiation in the University of California, Berkeley. A. Ghiorso, B. G. Harvey, G.R. Choppin, S.G. Thompson and G.T. Seaborg irradiated a small sample of einsteinium with 41 MeV helium ions, observing an isotope of element 101 with mass number 256.
These experiences deserve a special reference for the tiny dimension of the irradiated sample (Es 253) and consequently of the obtained product, and for the new irradiation techniques. Initially it was not detected any alpha particle activity that could indicate the presence of element 101; however, spontaneous fission of fermium was observed leading to a new element, proved in subsequent experiences to be the 101st. Based on this evidence, although indirectly, the investigators announced the discovery of element 101, suggesting the name mendelevium, in honor of Dimitri Mendeleev. Originally, the symbol of the mendelevium was Mv, this being later altered to the actual Md.
There are registers of producing mendelevium isotopes in the former-U.S.S.R through heavy ions reacting.
In 1967 the announcement of the discovery of Md 258 was made. This has a half-life of about two months, being the highest for a mendelevium isotope.