What is the term for a reaction in which a substance gains an electron

Every redox reaction consists of two parts, the oxidation and the reduction. Each one separately is called a half - reaction. During the redox reaction there is a transfer of electrons from the substance being oxidized to the substance being reduced.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.