Complete the statements given below by filling in the blank with the correct words.
The valency of iron in FeO is __________[`2^(+)//1^(+)]` of chlorine [chloride ] in `CaCl_(2)` is ___________`[1^(-)//2^(-)]` and of dichromate in `K_(2)Cr_(2)O_(7)` is _______`[2^(+)//2^(-)]`