Californium is a radioactive metal found in the actinide category of the periodic table. Its standard attomic weight is 251 and is elemenent numer 98. History
Californium was first synthesized at the University of California, Berkeley by the physics researchers Stanley G. Thompson, Kenneth Street, Jr., Albert Ghiorso, and Glenn T. Seaborg on or about February 9, 1950. It was the sixth transuranium element to be discovered; the team announced its discovery on March 17, 1950. To produce californium, a microgram-sized target of curium-242 (242/ 96Cm) was bombarded with 35 MeV-alpha particles (4/2He) in the 60-inch-diameter (1,500 mm) cyclotron at Berkeley, California, which produced californium-245 (245/ 98Cf) plus one free neutron (n). 242 245
96Cm + 4/2He → 98Cf + 1/0n
Only about 5,000 atoms of californium were produced in this experiment, and these atoms had a half-life of 44 minutes. The discoverers named the new element after California and the University of California. This was a break from the convention used for elements 95 to 97, which drew inspiration from how the elements directly above them in the periodic table were named. However, the element directly above element 98 in the periodic table, dysprosium, has a name that simply means "hard to get at" so the researchers decided to set aside the informal naming convention. They added that "the best we can do is to point out [that] ... searchers a century ago found it difficult to get to California." Weighable quantities of californium were first produced by the irradiation of plutonium targets at the Materials Testing Reactor at the Idaho National Laboratory; and these findings were reported in 1954. The high spontaneous fission rate of californium-252 was observed in these samples. The first experiment with californium in concentrated form occurred in 1958. The isotopes californium-249 to californium-252 were isolated that same year from a sample of...