Californium

Californium is named after the state of California and the University of California, Berkeley. First synthesized in 1950 by Stanley Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn Seaborg, only about 5,000 atoms were initially produced. Californium-252 is the most useful isotope, and it has some surprisingly practical applications for such a rare element.

Californium-252 spontaneously emits neutrons, making it invaluable for starting up nuclear reactors, detecting gold and silver ores, identifying metal fatigue in aircraft, and finding moisture and oil in soil and rock layers. It is used to treat certain types of brain and cervical cancer through neutron brachytherapy. Californium is one of the most expensive substances on Earth — californium-252 costs about $27 million per gram.

Californium's symbol 'Cf' is a distinctive two-letter element in Spellement. While 'cf' is uncommon in English words, partial emphasis lets spellers use 'c' or 'f' individually — both common consonants. This makes californium a flexible, if unusual, building block for creative word spelling.