What is an electron configuration?

Electron configuration is a way of showing how electrons are arranged in an atom’s orbitals.

• It tells which orbitals the electrons occupy and how many electrons are in each orbital.
• It follows three main rules:
  1. Aufbau principle – electrons fill lowest energy orbitals first.
  2. Pauli exclusion principle – an orbital can hold maximum 2 electrons with opposite spins.
  3. Hund’s rule – electrons occupy empty orbitals first, with parallel spins.

Example:

• Carbon (C, atomic number 6):
  • Electron configuration: 1s² 2s² 2p²
  • Means:
    • 2 electrons in 1s orbital
    • 2 electrons in 2s orbital
    • 2 electrons in 2p orbital

In short:
Electron configuration = the “address” of electrons in an atom’s orbitals.