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] The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate or hydroxide.[4] If problems of availability of the element could be overcome, then CfBr2 and CfI2 would likely be stable.[5]
The +3 oxidation state is represented by californium(III) oxide (yellow-green, Cf2O3), californium(III) fluoride (bright green, CfF3) and californium(III) iodide (lemon yellow, CfI3).[3] Other +3 oxidation states include the sulfide and metallocene.[6] Californium(IV) oxide (black brown, CfO2), californium(IV) fluoride (green, CfF4) represent the IV oxidation state. The II state is represented by californium(II) bromide (yellow, CfBr2) and californium(II) iodide (dark violet, CfI2).[3]