What is the Oxidation Number of the Sulphur Atom in Na2S2O3

Answer: 

Oxidation number-

Oxidation number can be defined as the total number of electrons that atoms in a molecule can lose, share or acquire while building a chemical interaction with atoms of other elements. 

Na2​S2​O3​ =

 The oxidation number of S1​= −2

The oxidation number of S2 ​= +1+1+2+2 = + 6

The average oxidation number of S= 2−2+ 6

= + 2