Chemical element "Sb" (stibium) for antimony. Chemical symbols are understood internationally when element names might require translation. There have sometimes been differences in the past. For example, Germans in the past have used "J" (for the alternate name Jod) for iodine, but now use "I" and "Iod". The first letter of a chemical symbol is always capitalized, as in the preceding examples, and the subsequent letters, if any, are always lower case (small letters). Thus, the symbols for californium and einsteinium are Cf and Es. There are also symbols in chemical equations for groups of chemical elements, for example in comparative formulas.
Californium made by bombarding berkelium-249 () with neutrons, forming berkelium-250 () via neutron capture (n,γ) which, in turn, quickly beta decays (β) to californium-250 () in the following reaction: Bombardment of californium-250 with neutrons produces californium-251 and californium-252. Prolonged irradiation of americium, curium, and plutonium with neutrons produces milligram amounts of californium-252 and microgram amounts of californium-249. As of 2006, curium isotopes 244 to 248 are irradiated by neutrons in special reactors to produce primarily californium-252 with lesser amounts of isotopes 249 to 255. Microgram quantities of californium-252 are available for commercial use through the U.S. Nuclear Regulatory Commission. Only two