An electron orbital is a region of space around the nucleus of an atom where an electron is most likely to be found. Orbitals are not well-defined paths. They represent regions of space where the probability of finding an electron is high.
The arrangement of electrons in shells and orbitals around an atom’s nucleus is governed by the Pauli exclusion principle.
The Pauli exclusion principle ensures each electron occupies a unique quantum state, defined by four quantum numbers (n, l, mℓ, and s).
No two electrons can occupy the same quantum state simultaneously, leading to the formation of distinct shells and orbitals within each shell.
The four quantum numbers (n, l, mℓ, and s) dictate the specific orbital position of an electron, with n indicating the main energy level, ℓ defining orbital shapes, mℓ determining orbital orientation, and s indicating electron spin.
A table illustrating the quantum numbers for various electron orbitals can be found here.