Chemistry class 12th Electronic_Configurations-1

Electronic Configurations - Detailed Explanation


### Atomic Structure & Orbitals
Electrons are arranged in orbitals around the nucleus of an atom. The orbitals are divided into
energy levels (shells)
represented by principal quantum numbers (n = 1, 2, 3, ...). Within each shell, there are sublevels: s,
p, d, and f orbitals.


### Aufbau Principle
The Aufbau principle states that electrons fill orbitals starting from the lowest energy level before
moving to higher levels.


### Pauli Exclusion Principle
No two electrons in an atom can have the same set of four quantum numbers. This means that an
orbital can hold a maximum
of two electrons with opposite spins.


### Hund's Rule
Electrons occupy orbitals of the same energy singly before pairing up. This minimizes electron
repulsion and increases stability.


### Notation & Examples
Electron configuration notation follows the pattern:
- Hydrogen (H): 1s1
- Oxygen (O): 1s2 2s2 2p4
- Iron (Fe): [Ar] 4s2 3d6


### Electronic Configurations of Elements
Each element has a unique electronic configuration that determines its chemical properties. For
example:
- Sodium (Na): 1s2 2s2 2p6 3s1
- Chlorine (Cl): 1s2 2s2 2p6 3s2 3p5