Sulfur (S) has an atomic number of 16. What would you expect its covalency to be? Why?
This is because of its 3p4 orbital. p-orbitals allow for 6 places to be filled, hence sulfur tends to form 2 bonds. It can “expand the octet” as it has 6 valence electrons, hence allowing the formation of 6 bonds. An example is SF6
but a simpler answer would be that it is in the same period as oxygen and has 6 valence electrons in its outer orbital, like oxygen, and prefers to have two bonds to satisfy the octet.