# What is oxidation number?

Nov 28, 2016

Oxidation number is the charge left on the central atom, when all the bonding pairs are removed with the charge going to the most electronegative atom.

#### Explanation:

So for $\text{sulfate anion}$ we have, FORMALLY, ""^(-)O-S(=O)_2O^-. The oxidation number of oxygen is usually $- I I$ and it is here.

Thus ${S}_{\text{ON}} + 4 \times \left(- 2\right) = - 2$; clearly, ${S}_{\text{ON}} = + V I$. Oxygen gets both electrons from a $S - O$ bond because it is more electronegative than sulfur.

For arsenic sulfide, $A {s}_{2} {S}_{3}$, which is think is used by artists as the vivid yellow pigment, $\text{King's yellow}$, sulfur is now bound to an element whose electronegativity is LESS than its own and thus sulfur is here an analogue of oxygen, and assumes a ${S}^{- 2}$ i.e. $S \left(- I I\right)$ oxidation state; i.e. here it is an oxide analogue; and we necessarily have $A s \left(+ I I I\right)$ centres.

What is the oxidation state of elemental sulfur, ${S}_{8}$?