Question

If the electronic configuration of nitrogen atoms is represented as shown below, then which of the following rules have been violated?

(A) Aufbau’s principle
(B) Pauli’s exclusion principle
(C) Hund’s rule
(D) None of the above

Answer 1

Hint: Arrangement of electrons in the orbitals and in the subshells can be guided using different laws. To completely describe an electron in an atom, four quantum numbers are needed: principal quantum number, angular momentum, magnetic moment and spin.

Complete step by step answer:
To know which of the rules is violated we will discuss each rule given in the option.
Considering option A, Aufbau’s principle. The Aufbau’s principle dictates the manner in which electrons are filled in the atomic orbitals of an atom in its ground state. It states that electrons are filled into an atomic orbital in the increasing order of orbital energy level. According to the Aufbau principle, the available atomic orbitals with the lowest energy levels are occupied before those with higher energy levels. Since there is no violation of this rule in filling of the orbitals, therefore, option A is not correct.

Considering option B, Pauli exclusion principle. The pauli exclusion principle states that no two electrons in the same atom can have identical values for all four of their quantum numbers.In other words, we can say that (1) No more than two electrons can occupy the same orbital and (2) two electrons in the same orbital must have opposite spins. We can clearly see that this law is violated in the given arrangement, as two electrons are filled in the same orbital with the same spin in 2p orbital.

Considering option C, Hund’s rule. The Hund’s rule states that, Every orbital in a sublevel is singly occupied before any orbital is double occupied, and All of the electrons in singly occupied orbitals have the same spin. We can see that this law is also violated, as electrons are not filled in every subshell in 2p orbital, one subshell is doubly filled with electrons and one subshell is left empty.
So, the correct answer is “Option B and C”.

Note: There can be maximum two electrons in one subshell. The s-orbital has one subshell, and can contain maximum 2 electrons with opposite spins. The p-orbital has 3 subshells and can contain maximum 6 electrons with opposite spins.