Octet rule is mostly violated in the compounds formed by

(A) alkali metals

(B) alkaline earth metals

(C) p–block elements

(D) transition elements

In case of transition elements, 3d orbitals also available for bonding. In a number of compounds of these elements there are more than eight valence electrons around the central atom. This is termed as the expanded octet. Obviously the octet rule does not apply in such cases. In p-block elements except 2nd period elements d - orbitals are available and expanded octet is observed.