Question

please guys answer it . Why sulphur has variable valencies?

Answer 1

There are four atomic orbitals namely s,p,d and f and electrons are distributed
among these orbitals only. Sulphur comes in 3rd period of periodic table and it 
contains s,p and d orbital only.
In the ground state, the d orbital remains empty, when excitation occurs there
is jumping of paired electrons to the d orbital and therefore they show an 
increase in valency or variable valency.
For example :
In SO2, valency of sulphur is 4, while in SOCl​2it is 6.