Define octet rule. Write its significance and limitations.

The tendency of atoms to complete eight electrons in their outer shell by interacting with other atoms through electron sharing or electrons transfer is known as the octet rule of chemical bonding.

Significance:
1. Octet rules able to explain chemical bonding in various compounds.
2. Octet rules able to illustrate the various type of bonds like a covalent, electrovalent and coordinate bond.
Limitation:
The octet rule is not satisfied for all atoms in a compound.
1. Compounds which have an incomplete octet of the central atoms.
LiCl, BeH₂, BCl₃, AlCl₃,BF₃, LiBr, AlBr_3.

2.The rule failed to predict the shape and relative stability of molecules.
3. Octet rule fails to explain why in some compounds more than eight electron is there on central atom:
Compounds like PF₅, SF₆.
4. It is based upon the inert nature of noble gases. However, some noble gases like xenon and krypton form compounds such as XeF₂, KrF₂ etc.