Name: Hybridisation in SF₆ Molecule
Uploaded: 2019-07-19
Duration: 2 min 31 s
Description: Understand the bonding present in the case of sulphur hexafluoride. This video illustrates that the hybridisation present in the case of sulphur hexafluoride...

Question

What is octet rule? Briefly explain its significance and limitations.

Accepted Answer

Atoms of various elements can combine either by transfer of valence electron from one atom to another (gaining or losing) or by mutual sharing of valence electrons in order to attain the stable configuration of eight electrons in their outermost shell. This is known as octet rule.

Significance of octet rule: It explains the reason behind the chemical combination of different atoms to form ionic or covalent bond.

Limitations of octet rule:

(i) Hydrogen with an electron attains stability by sharing, gaining or losing one valence electron. It does not need to complete its octet to attain the stability. Also, helium atom has only two electrons and is stable.
(ii) Incomplete octet of the central atom: In certain molecules such as ${BeH}_{2}$ , $LiCl$ and ${BCl}_{3}$ , the central atom has less than eight electrons in its valence shell, yet the molecules are stable.
(iii) Expanded octet: In certain molecules such as ${PF}_{5}, {SF}_{6}, {IF}_{7}$ and $H_{2} {SO}_{4}$ , the central atom has more than eight valence electrons, but these molecules are stable.

(iv) Odd-electron molecules: In certain molecules such as $NO$ and ${NO}_{2}$ , the octet rule is not satisfied for all the atoms.

What is octet rule? Briefly explain its significance and limitations.

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