Question

What is the oxidation number for each atom? (NH4)2Ce(SO4)3.

All numbers are supposed to subscripts.

Answer 1

Subscripts?.......We commonly superscript the oxidation number.

Explanation:

We have the `Ce(IV)` salt, `(NH_4^+)_2[Ce(SO_4)_3]^(2-)`, `"ceric ammonium sulfate"`

Now the sum of the oxidation numbers equals the charge on the ion. For `NH_4^+` we gots `4xxstackrel(+I)H`, and `1xxstackrel(-III)N`; the sum of the oxidation numbers is `+1` as required for the ammonium ion.

And for the ceric salt, we gots `stackrel(+IV)"Ce"`, and `stackrel(VI^+)S` and `stackrel(-II)O`: `4+3xx6-24=-2` as required for `[Ce(SO_4)_3]^(2-)`

See here for general rules.

And see here for another example of assignment of oxidation number.