I) II) Why do the s orbitals on H and Na not combine to form a strong covalent bond? Solution I) 2p orbitals are compact and concentrated and also they are closer together making the “sideways†overlap of their \'p\' atomic orbitals that much better.Pi bonds are side to side bonds, large atoms hinder close approach. So that Pi bonds in C atoms are stronger than Pi bonds in Pb atoms. II) H atom can accept one electron and Na can donate one electron and becoming H - and Na + .These two atoms never share their electron, so that there is no formation of covalent bond. Na atom is strong electropositive atom. .