Which characteristic do valence electrons indicate about reactions between atoms?

Bond number

The characteristic of reactions that depends on valence electrons is the bond type.

In chemistry, a chemical bond could be;

Ionic

Covalent

The type of bond formed depends on the number of valence electrons present. When there are few valence electrons on an atom, it mostly forms ionic bonds.

When there are more electrons on an atoms, it mostly forms covalent bonds and the electrons between the atoms are shared.

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.