Define octet rule and write its significance and limitations.

Explanation:

The noble gas configuration is the most stable and every element tries to have a noble gas configuration.

According to the octet rule, atoms tend to form compounds with eight valence electrons, resulting in the electron configuration of a noble gas.

Significance:

The octet rule depicts chemical bonding types such as covalent, ionic, and coordinate bonds.

Limitations:

In some molecules such as BeH₂, BH₃, and BF₃ despite the fact that the core atom's valence shell has less than 8 electrons, the molecule is stable.

In some molecules such as SF₆, IF₇, and PF₅ despite the fact that the core atom's valence shell has more than 8 electrons, the molecule is stable.

The octet rule was also unable to predict the structure of the molecules or their relative stability.

Final answer: 

In some molecules such as BeH₂, BH₃, and BF₃ despite the fact that the core atom's valence shell has less than 8 electrons, the molecule is stable.

In some molecules such as SF₆, IF₇, and PF₅ despite the fact that the core atom's valence shell has more than 8 electrons, the molecule is stable.

The octet rule was also unable to predict the structure of the molecules or their relative stability.