Question

What are Hund’s rules, Pauli Exclusion Principle, and Aufbau principle? How are they different? How are they related?

Answer 1

Hint: As we know that the quantum numbers help us to define the location of an electron within the atomic structure. It is found that these electrons of an atom do not fill its shells and subshell randomly, but they follow a particular order, that was mainly followed by three rules that are Hund’s rule, Pauli Exclusion Principle, and Aufbau principle.

Complete answer:
- Let’s discuss in brief about Hund’s rule, Pauli Exclusion Principle, and Aufbau principle
- Aufbau principle: according to this principle the lower energy orbitals are filled before higher energy orbitals.
 - Hund’s rule: It says that one electron goes into each subshell until all of them are half full before pairing up.
- Pauli Exclusion principle: no two electrons can be identified by the same set of quantum numbers
- 2K,8L,9M, and 2N electrons are given and we know that K, L, M, N are the shells and the numbers that are 2,8,9,2 represents the number of electrons that are present in the particular shell. And s, p, d, f are the subshells and l represents the number of subshells.
- These principles together help us to write the electronic configurations and to draw the energy diagrams.

Note:
- As we know that in Aufbau principle lower energy orbitals are filled before higher energy orbitals. And according to Hund’s rule one electron goes into each until all of them are half filled before pairing up. According to Pauli exclusion principle two electrons must have opposite spins.