redox - Why are electrons shared equally when calculating formal charge, but unequally when calculating oxidation state?

• When calculating formal charge - electrons are shared equally between the atoms in the bond.


• When calculating oxidation state - electrons are both given to the most electronegative atom.

Why is this different?

I am assuming it is something to do with the intended use of calculating formal charge and oxidation state, which I believe are:

• Formal charge can be used to find the most stable structure.


• Oxidation numbers can be used to determine what will become oxidised in a redox reaction.

However, even based on their uses, I am unsure why they are calculated differently.

*Images from Wikipedia