Question

State and illustrate Pauli’s exclusion principle.

Answer 1

Hint: Pauli’s exclusion principle, Hund’s rule of maximum multiplicity and Aufbau principle is the three important theories related to the structure of an atom. Every atom and electrons in it should follow these three important principles.

Complete step by step answer:
When we started studying the structure of atoms, we studied about protons, neutrons, electrons and how these are arranged in an atom. So, there are certain laws that each electron should follow when it becomes part of an atom. Such a principle is that the Pauli’s Exclusion Principle. It states that no electrons should have not the same quantum numbers. More clearly, if we look at the first shell, it only contains two electrons in the first subshell. The principal quantum number, azimuthal quantum number and magnetic quantum numbers are the same for this electron. The last quantum number must be different, that means the electrons should be in different spins. So, they will get unique quantum numbers. No two electrons will possess the same quantum numbers according to this rule.

Additional Information:
Aufbau principle states that electrons are filled in the atomic orbitals of an atom in its ground state. It states that electrons are filled into atomic orbitals in the increasing order of orbital energy level.
The problem with the Aufbau principle is that it does not tell about the three 2p orbitals and the order that they will be filled in.
According to Hund’s rule, before the double occupation of any orbital, every orbital in the sub level is singly occupied.
For the maximization of total spin, all electrons in a single occupancy orbital have the same spin.

Note: You should not confuse three rules that are Aufbau principle, Hund’s rule and Pauli’s exclusion principle. Use any tricks to memorize these three rules distinctively.