Structure of Atom

Aufbau Principle, Pauli's Exclusion Principle and Hund's Rule

Aufbau Principle:

According to this principle, in the ground state of an atom, the electrons occupy the lowest energy orbitals available to them, i.e. the orbitals are filled in order of increasing value of n + l. For the orbitals having the same value of n + l, the orbital having lower value of n is filled up first.

Pauli Exclusion Principle:

It states, no two electrons in an atom can have identical set of four quantum numbers.
The maximum number of electrons in s subshell is 2, p subshell is 6, d subshell is 10 and f subshell is 14.

Hund's Rule of Maximum Multiplicity:

It states,

(i) In an atom no electron pairing takes place in the p, d or f-orbitals until each orbital of the given subshell contains one electon.
(ii) The unpaired electrons present in the various orbitals of the same subshell should have parallel spins.

View the Topic in this Video from 0:40 to 39:35

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