After the war , Seaborg and Ghiorso returned to Berkeley , where they and colleagues used the 60 " Crocker cyclotron to produce elements of increasing atomic number by bombarding exotic targets with helium ions . In experiments during 1949-1950 , they produced and identified elements 97 ( berkelium ) and 98 ( californium ) . In 1953 , in a collaboration with Argonne Lab , Ghiorso and collaborators sought and found elements 99 ( einsteinium ) and 100 ( fermium ) , identified by their characteristic radiation in dust collected by airplanes from the first thermonuclear explosion ( the Mike test ) . In 1955 , the group used the cyclotron to produce 17 atoms of element 101 ( mendelevium ) , the first new element to be discovered atom-by-atom . The recoil technique invented by Ghiorso was crucial to obtaining an identifiable signal from individual atoms of the new element
Mike test
Ivy Mike
Albert Ghiorso