# why colour of CuSO4 and CuCl3 is different? [duplicate]

These two are simple ionic compounds , not complexes [if I do not consider water of hydration] then how can I rationalise the difference in colour?

• Cu3+ is still a different color than Cu2+, isn't it? – Lighthart Mar 13 '15 at 6:05
• @Lighthart Honestly, I've never seen copper(III) in solution. Have you? It's not that copper(III) wouldn't exist, such as in ores, but as a naked, solvated cation? – Klaus-Dieter Warzecha Mar 13 '15 at 6:19
• Do you really mean $\ce{CuCl3}$ or is it just a typo and you thought in $\ce{CuCl2}$? On a second note, copper(II)sulfate itself undergoes a colour change when converting the pentahydrate to the anhydrous form. – Klaus-Dieter Warzecha Mar 13 '15 at 6:37
• LIGAND FIELD THEORY. Colors in these ions are based on electron transitions between non-degenerate d-orbitals. The energy of these transitions (thus the color) is a function of the metal oxidation state, the type of ligand/counterion, and the molecular geometry. Hydration or not d-orbitals are still going to distort based on those factors. – StevieD Mar 25 '16 at 6:32