What are #"oxidation state"#, or #"oxidation number"#?

#"Oxidation/state"# number is the charge left on the atom of interest, when all the bonding pairs of electrons are broken with the charge assigned to the most electronegative atom.

See [here for determination.](https://socratic.org/questions/how-can-an-oxidation-number-be-determined?source=search)

Note that this is a conceptual exercise, and the rules for assigning oxidation states are fairly arbitrary and abstract. Note that elements have NEITHER accepted NOR donates electrons, and for a simple redox equation (the one which follows heats our homes, and cooks our food), the oxidation states of the reactants are ZERO:

#stackrel(0)C(s)+stackrel(0)O_2(g)rarrstackrel(+IV)Cstackrel(-II)O_2(g)#

Oxygen typically adopts an oxidation state of #-II# in its compounds (its #"oxides"#, but not #"peroxides"#), i.e. it reflects the #O^(2-)# ion. Carbon can adopt any oxidation state from #-IV# to #+IV#. For instance #stackrel(-IV)CH_4#, #H_3stackrel(-III)C-CH_3#, #H_3stackrel(-III)C-stackrel(-II)CH_2CH_3#, and pervalent #CO_2#. When we encounter a #C-C# chain, we assume that the electrons are shared equally between the carbon atoms of equal electronegativity:

#H_3C-CH_3rarr2xxH_3C*rarr3xxH^(+I) + C^(-III)#.

#(H_3C)_4Crarr4xxH_3C*+:C:rarr3xxH_3C^(-III) + C^(0)#.

I reiterate that this is a CONCEPTUAL exercise. The assignment of oxidation numbers is sometimes useful for the purposes of stoichiometry; it does not reveal much insight as to electronic structure.