Final answer:
The formal charges of each element in the given compounds and ions are: CH4 (hydrogen: 0, carbon: 0), NO3⁻ (oxygen: -1, nitrogen: +1), H2CO (hydrogen: +1, carbon: 0, oxygen: -1), SO4²⁻ (oxygen: -2, sulfur: 0).
Step-by-step explanation:
(a) CH4:
Each hydrogen atom in CH4 has a formal charge of 0, since hydrogen tends to lose one electron to achieve a stable configuration. Carbon has a formal charge of 0 as well, since it has four valence electrons and it shares all electrons equally with the hydrogen atoms.
(b) NO3⁻:
In NO3⁻, each oxygen atom has a formal charge of -1 since oxygen is more electronegative than nitrogen. Nitrogen, as the central atom, has a formal charge of +1. The overall formal charge of the ion is -1.
(c) H2CO:
The carbon atom in H2CO has a formal charge of 0, while the two hydrogen atoms each have a formal charge of +1. The oxygen atom has a formal charge of -1.
(d) SO4²⁻:
The sulfur atom in SO4²⁻ has a formal charge of 0, while each oxygen atom has a formal charge of -2. The overall formal charge of the ion is -2.