Question

How does the concept of formal charge related to the stability of ion/molecule?

Answer 1

Atoms become formally charged on the basis of their relative stability,

In case of non-metals, (which is from the right-hand side of the Periodic Table), we have high nuclear charge and they tend to be oxidized, i.e. they accept electrons to form anions

$\frac{1}{2} F_{2}+e^{-}\rightarrow F^{-}\\\frac{1}{2}O_{2}+2e^{-}\rightarrow O^{2-}$

In case of metals the electron rich or powerful and they tend to be reduced and form cations

$M\rightarrow M^{2+}+2e^-$

The basic chemistry involves the formation of stable salt with the combination positive and negative ions.