Define electronic configuration?

Electronic configuration is the arrangement of electrons in different shells and subshells of an atom according to increasing energy levels.

Each atom’s electrons occupy shells (K, L, M, N) or energy levels denoted by quantum numbers. Electrons fill from lower to higher energy orbitals following the Aufbau principle, Pauli exclusion principle, and Hund’s rule. For example, oxygen (atomic number 8) has configuration 1s² 2s² 2p⁴. This arrangement explains chemical reactivity and periodic table trends like valency and bonding. 

Examples

• Hydrogen (1): 1s¹
• Carbon (6): 1s² 2s² 2p²
• Sodium (11): 1s² 2s² 2p⁶ 3s¹