Quantum numbers are of basic physical importance in quantum physics. In the early 1900s energy in atomic systems was found to exist as quanta or discrete, indivisible units. This concept along with the particle-wave duality led to the development of quantum physics and hence the Schrödinger equation. Unlike classical mechanics, in which energy is continuous and electrons follow fixed orbits described by Bohr's planetary model, quantum mechanics describes electrons as effectively taking up entire predefined spaces around the nucleus and energy as a quantized phenomenon. Quantum numbers are the four numbers used to describe not only the distribution of electrons in atoms and molecular systems but also the allowable values of certain physical quantities of an electron's behavior. A wave function for an electron describes the probability of finding that electron at various points in space. The first three quantum numbers describe the physical...