Question

Explain Paul is Exclusion Principle and Aufbau principle

Answer 1

Paulis exclusion principle:-No two electrons in an atom can have all the four quantum
numbers same.
Aufbaus rule:-aufbau is a German word which means to build up.Basically we have to build up the electronic configuration of atoms. This rule states that only those energy states are filled first with lower values of(n+l) bcz those energy states with lower (n+l)have lower energy.If two or more energy states have same values of (n+l) then the state with lower n has lower energy&is filled first.
Hope it will help you.

Answer 2

Hi .

Pauli Exclusion Principle
So, according to these rules, if we look at the first shell, it only contains two electrons in the first subshell. The quantum number can be described as 1s^2. However, another rule is that two electrons cannot have identical quantum numbers. So, if two electrons have to fit inside one s subshell, how will this work?

This matter directly relates to the Pauli Exclusion Principle, which states that two electrons cannot exist in the same location and thus electrons in the same orbital must have opposing spins. Hydrogen only has one electron in the 1s orbital and has a quantum number of 1s^1. Helium has two electrons in this field, so they must have opposing spins, and it has a quantum number of 1s^2.

This spin factor is the fourth quantum number, m, and is described as either +1/2 for a spin 'up' or -1/2 for a spin 'down.'

Aufbau Principle
Closely related to Hund's Rule is the Aufbau Principle, which states that electrons will fill the lower energy levels before moving to higher energy orbitals. Remember that each orbital has two electrons and the number of orbitals at an energy level depends on the first two quantum numbers.