David W. Oxtoby Quote

Quantum mechanics explains the physical stability of the atom by predicting its allowed discrete energy levels and defining the wave functions (also called atomic orbitals) associated with each energy level. The orbitals determine the probability density for finding the electrons at particular locations in the atom when the electrons are in a specific quantum state.

Principles of Modern Chemistry (7th ed., 2012) - Ch. 5 : Quantum Mechanics and Atomic Structure