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Few compounds of californium have been made and studied. [1] The only californium ion that is stable in aqueous solutions is the californium(III) cation. [2] The other two oxidation states are IV (strong oxidizing agents) and II (strong reducing agents). [3]
Californium is a silvery-white actinide metal [12] with a melting point of 900 ± 30 °C (1,650 ± 50 °F) and an estimated boiling point of 1,743 K (1,470 °C; 2,680 °F). [13] The pure metal is malleable and is easily cut with a knife. Californium metal starts to vaporize above 300 °C (570 °F) when exposed to a vacuum. [14]
This occurs because of the much greater lattice energy afforded by the more highly charged Ca 2+ cation compared to the hypothetical Ca + cation. [10] Calcium, strontium, barium, and radium are always considered to be alkaline earth metals; the lighter beryllium and magnesium, also in group 2 of the periodic table, are often included as well.
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.
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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.
Californium(III) oxide forms a yellow-green solid with a melting point of 1750 °C and exists in three modifications. [2] The body-centered cubic modification forms a crystal lattice with a = 1083.9 ± 0.4 pm. The transition temperature between body-centered cubic and monoclinic structures is about 1400 °C. [3] [4] It is insoluble in water. [5]
This page was last edited on 16 February 2022, at 01:13 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.