For an atom that becomes an ion, does it have a formal charge, or net charge? What is the difference between formal charge, oxidation state, and net charge?

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For an atom that becomes an ion, does it have a formal charge, or net charge? What is the difference between formal charge, oxidation state, and net charge?

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Answer 1 · 2016-07-21T21:40:41

For an atom that just became an ion, like $O^{2 -}$ $"O"^(2-)$ , that is not its formal charge, but it is its net charge.

Formal charge is the hypothetical charge for an atom when assuming that electrons are perfectly evenly shared in a chemical bond.

It's not the same as an oxidation state; it's pretty much the complete opposite.

Strictly speaking, $O^{2 -}$ $"O"^(2-)$ doesn't have a formal charge because it's not within the context of a molecule.
In ${CO}_{2}$ $"CO"_2$ , we have $: . . O = C = . . O :$ $:stackrel(..)"O"="C"=stackrel(..)"O":$ . The formal charge on $C$ $"C"$ is $0$ $0$ , and the formal charge on each $O$ $"O"$ is $0$ $0$ . We can say that because the atoms are in the context of a molecule.

Oxidation state is the hypothetical charge for an atom when assuming that electrons would be completely transferred from one atom to another in a chemical bond.

If you look at a lone atom, its charge is its oxidation state. The oxidation state of the $O^{2 -}$ $"O"^(2-)$ anion is $- 2$ $color(blue)(-2)$ , the same as its charge, $2 -$ $2-$ .
The oxidation state of $O$ $"O"$ in ${CO}_{2}$ $"CO"_2$ would be $- 2$ $-2$ , so the oxidation state of $C$ $"C"$ in ${CO}_{2}$ $"CO"_2$ would be $+ 4$ $+4$ . We write that as $+ 4 C - 2 O_{2}$ $stackrel(+4)("C")stackrel(-2)("O"_2)$ . It does not mean that carbon has given away all of its $n = 2$ $n = 2$ valence electrons.

Net charge is simply the total charge on an atom or molecule or compound.

For $O^{2 -}$ $"O"^(2-)$ , it's only one atom, so its net charge is its actual charge, $2 -$ $color(blue)(2-)$ .
For $: δ^{-} C \equiv δ^{+} O :$ $:stackrel(delta^(-))("C")-=stackrel(delta^(+))("O"):$ , the net charge is $0$ $0$ , because the formal charge on $C$ $"C"$ is $- 1$ $-1$ , and the formal charge on $O$ $"O"$ is $+ 1$ $+1$ , so $- 1 + 1 = 0$ $-1+1 = 0$ .

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For an atom that becomes an ion, does it have a formal charge, or net charge? What is the difference between formal charge, oxidation state, and net charge?

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