Question

What is the oxidation number of sulphur? Give an example.

Answer 1

Hint : Oxidation number of an atom can be defined as the number of electrons that the atom gains or loses while forming chemical bonds or the charge that the atom will form if the compound was composed of ions.

Complete Step By Step Answer:
The oxidation number of sulphur depends upon the compound that it forms. It shows many oxidation numbers according to the compound formed.
Sulphur shows oxidation numbers of $ - 2,0, + 2, + 4 $ and $ + 6 $
Sulphur shows oxidation number of $ - 2 $ in $ {H_2}S $ .(Hydrogen sulphide gas has a characteristic rotten egg smell)
 $ {H_2}S = 2\left( 1 \right) + X = 0 $ (Oxidation number of hydrogen is 1)
 $ X = - 2 $ (oxidation number of sulphur was found to be -2)
Sulphur shows zero oxidation number in its elemental form (It is a yellow solid)
 $ {S_8} $ (sulphur has zero oxidation number)
Sulphur shows $ + 6 $ oxidation state in $ {H_2}S{O_4} $
= $ 2\left( 1 \right) + X + 4\left( { - 2} \right) $
 $ X = 6 $
Similarly, we can see other examples as well : In $ N{a_2}{S_2}{O_6} $ , Sulphur shows $ + 5 $ oxidation state,
 In $ N{a_2}{S_2}{O_3} $ , sulphur shows $ + 2 $ oxidation state.

Additional Information:
Sulphur forms covalent bonds to partner atoms at oxidation states $ - 2, + 2, + 4, + 6 $ . Sulphur is found in abundance in earth crust as dianion of sulphuric acid in which sulphur is present in oxidation state of $ + 6 $ . Sulphur makes up approximately three percent of the earth’s mass.

Note :
Sulphur shows such a wide range of oxidation numbers. It shows different oxidation numbers in different compounds. The sum of the oxidation numbers of all elements in a polyatomic ion is equal to the charge on the ion.