Chemical bonding in the perchromate ion

The perchromate ion, CrO83-, in K3CrO 8 has D2d (42m) symmetry and consists of a central pentavalent chromium ion surrounded by four peroxide groups. On the basis of a refinement of the previous structure determination, the chromium ion is nearer to one oxygen of each peroxide group than to the other and the peroxide oxygen-oxygen distance is shorter than normal. A ligand field calculation, based on the optical spectrum and the electron paramagnetic resonance spectrum, accounts for these structural features and leads to a description of the bonding in the perchromate ion.