If the electronic configuration of C is 2s6 then which rule(s) is/are violated?
If the electronic configuration of C is 2s6 then which rule(s) is/are violated?
The correct option is D Both (A) and (C)
Explanation: There are rules that has to be followed in order of filling of electrons.
Rule 1. The orbitals with lowest energy must be filled first. Order of filling electrons in the orbitals follow the pattern 1s, 2s, 2p, 3s, 3p, 4s, 3d, etc. This rule was known as AufBau's Rule.
Rule 2. In an orbital, only two electrons are permitted and they should have opposite spin. This rule simply means that no two electrons can have all the 4 quantum numbers same. This rule was known as Pauli Exclusion Principle.
Rule 3. The electrons are singly filled first in each orbital having same spin, then only pairing occurs. This rule was known as Hund's Rule.
For the given electronic configuration: 
The filling of electrons are filled according to AufBau's Rule which is the orbitals with lowest energy is filled first. But the first electron should be filled in 1s rather than 2s. Hence, this violates Pauli's Exclusion principle and further Hund's Rule.
Explanation: There are rules that has to be followed in order of filling of electrons.
Rule 1. The orbitals with lowest energy must be filled first. Order of filling electrons in the orbitals follow the pattern 1s, 2s, 2p, 3s, 3p, 4s, 3d, etc. This rule was known as AufBau's Rule.
Rule 2. In an orbital, only two electrons are permitted and they should have opposite spin. This rule simply means that no two electrons can have all the 4 quantum numbers same. This rule was known as Pauli Exclusion Principle.
Rule 3. The electrons are singly filled first in each orbital having same spin, then only pairing occurs. This rule was known as Hund's Rule.
For the given electronic configuration:
The filling of electrons are filled according to AufBau's Rule which is the orbitals with lowest energy is filled first. But the first electron should be filled in 1s rather than 2s. Hence, this violates Pauli's Exclusion principle and further Hund's Rule.
