Cerium
Halides

Cerium forms all four trihalides CeX (X = F, Cl, Br, I) usually by reaction of the oxides with the hydrogen halides. The anhydrous halides are pale-colored, paramagnetic, hygroscopic solids. Upon hydration, the trihalides convert to complexes containing aquo complexes. Unlike most lanthanides, Ce forms a tetrafluoride, a white solid. It also forms a bronze-colored diiodide, which has metallic properties. Aside from the binary halide phases, a number of anionic halide complexes are known. The fluoride gives the Ce(IV) derivatives CeF 4− 8 and CeF 2− 6. The chloride gives the orange CeCl 2− 6.
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