Define octet rule. Write its significance and limitations.

Octet rule states that “Atoms can combine either by the transfer of valence electrons from one atom to another by losing, sharing or gaining to acquire noble gas configuration (to complete octet in the outermost shells)”

Significance:

⇒With the help of octet rule, we can find out the nature of the bond.

⇒Octet rule helps out in providing a picture of bonding in molecules.

⇒It is useful for understanding the structure of most of the organic compounds.

Limitations:

⇒The incomplete octet of the central atom

It has been observed that in some compounds, the number of electrons around the central atom is less than 8. For example, in BCl₃

The number of electrons surrounding the central atom boron is less than eight. Some other such compounds are AlCl₃, BF₃, LiCl, BeH₂ etc.

⇒Odd-electron molecules

In compounds like NO and NO₂^-, which have odd number of electrons around the central atom N,