Question

What is octet configuration?

Answer 1

Elements which follow octet rule or octet configuration tends to attain eight electrons in their valence shell or outermost shell.

Complete step by step solution:
- The Octet rule is also known as Kossel Lewis concept. It explains the tendency of an atom to complete eight electrons in its outermost shell or valence shell. For this the atom does so by the sharing of electrons like Carbon atoms or by gain of electrons like Fluorine or by loss of electrons like Sodium atoms. So in order to attain eight electrons in a valence shell, the atom tends to lose, gain or share its valence electrons. For example electronic configuration of Sodium is $1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}3{{\text{s}}^1}$ which means according to octet rule Sodium will lose one electron to have eight electrons in its valence shell. So, ${\text{N}}{{\text{a}}^ + } = 1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}$.
- Similarly electronic configuration of Fluorine is $1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^5}$ which means according to octet rule Fluorine will tend to gain one electron in order to have eight electrons in its valence shell. So, ${{\text{F}}^ - } = 1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^6}$.
- The electronic configuration of Carbon is $1{{\text{s}}^2}2{{\text{s}}^2}2{{\text{p}}^4}$ which means according to octet rule Carbon atom tends to share four electrons with another atom to make eight electrons in its valence shell.

Exceptions of octet rule:
Odd electron species like ${\text{NO}},{\text{N}}{{\text{O}}_2},{\text{Cl}}{{\text{O}}_2},{\text{Cl}}{{\text{O}}_3},{\text{O}}_2^ -$ do not follow octet rule.
Electron deficient species or hypervalent compounds have less than eight electrons in their valence shell in their compound state. For example ${\text{Be}}{{\text{H}}_2},{\text{BC}}{{\text{l}}_3},{\text{AlC}}{{\text{l}}_3},{{\text{B}}_2}{{\text{H}}_6}$ and etc.
Super octet compound or hypervalent compounds have more than eight electrons in their valence shell in their compound state. For example ${\text{PC}}{{\text{l}}_5},{\text{S}}{{\text{F}}_4},{\text{S}}{{\text{F}}_6},{\text{Xe}}{{\text{F}}_2},{\text{Xe}}{{\text{F}}_6},{\text{I}}{{\text{F}}_7}$ and etc.

Note: According to valence bond theory, any atom which undergoes covalent bond formation tries to pair up its unpaired electron in ground state or excited state. This pairing of electrons takes place by the combination of two atomic orbital of two atoms having unpaired electrons.