Question

How do you calculate the oxidation state of carbon?

Answer 1

Carbon is the element of the second period of the periodic table. It is a very versatile element which combines with other atoms to form different compounds. In each compound the oxidation state of the carbon is different, and it depends on another atom with which it combines.

Complete step-by-step answer: Oxidation number, also called an oxidation state, represents the total number of electrons gained or lost to form a chemical bond.
Oxidation state of an element in different compounds is different and it depends on another atom which combines with it to form a bond.
Let us see the oxidation state of carbon in different cases.
$1$. The oxidation state of carbon in its elemental form is zero.
$2$. If Carbon forms a bond or compound by combining with a more electronegative element than itself, then the oxidation state of the carbon will always be positive because the more electronegative element with attract the electron towards itself, thus developing a partial negative charge on itself and following it a positive oxidation state on carbon and negative oxidation state on itself.
For example: In $C{{O}_{2}}$ carbon is attached with a more electronegative oxygen atom. As a result, it develops +4 oxidation state whereas oxygen has -4 oxidation state.
$3$. If carbon forms a bond by combining itself, that means if it forms $C-C$ bond, then in such cases the oxidation state of carbon is zero because both are similar atoms and thus will not gain or lose electrons.
$4$. In a $C-H$ bond, the $H$ is taken as if it has an oxidation state of $+1$. This means that every $C-H$ bond will decrease the oxidation state by $1$.
For example, in $C{{H}_{4}}$ the oxidation state of hydrogen is considered as $+1$ and so the oxidation state of carbon becomes $-4$ $\left( -1\,from\,each\,carbon \right)$

Note: It should be noted that unlike metals, which are almost always in a positive oxidation state, a carbon is much versatile and combines with various other elements to form bond and as a result its oxidation state varies from ${-4}$ to ${+4}$.