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Californium slowly tarnishes in air at room temperature. Californium compounds are dominated by the +3 oxidation state. The most stable of californium's twenty known isotopes is californium-251, with a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust.
32 of these have names tied to the Earth and the other 10 have names connected to bodies in the Solar System. The first tables below list the terrestrial locations (excluding the entire Earth itself, taken as a whole) and the last table lists astronomical objects which the chemical elements are named after.
Californium(III) oxychloride (CfOCl) was the first californium compound to be discovered. [15] Californium(III) polyborate is unusual in that californium is covalently bound to the borate. [16] Tris(cyclopentadienyl)californium(III) (Cp 3 Cf) presents itself as ruby red crystals.
Found on Earth in trace quantities by Olavi Erämetsä in 1965; so far, promethium is the most recent element to have been found on Earth. [194] 97 Berkelium: 1949 G. Thompson, A. Ghiorso and G. T. Seaborg (University of California, Berkeley) Created by bombardment of americium with alpha particles. [195] 98 Californium: 1950 S. G. Thompson, K ...
[5] [6] Synthetic elements now present on Earth are the product of atomic bombs or experiments that involve nuclear reactors or particle accelerators, via nuclear fusion or neutron absorption. [7] Atomic mass for natural elements is based on weighted average abundance of natural isotopes in Earth's crust and atmosphere. For synthetic elements ...
Californium (98 Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245 Cf in 1950. There are 20 known radioisotopes ranging from 237 Cf to 256 Cf and one nuclear isomer, 249m Cf.
The 20 isotopes of californium with mass numbers 237–256 are formed in nuclear reactors; [58] californium-253 is a β-emitter and the rest are α-emitters. The isotopes with even mass numbers ( 250 Cf, 252 Cf and 254 Cf) have a high rate of spontaneous fission, especially 254 Cf of which 99.7% decays by spontaneous fission.
It is the fifth most abundant element in Earth's crust, and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate , found in limestone and the fossilized remnants of early sea life; gypsum , anhydrite , fluorite , and apatite are also sources of calcium.