The quantum is the basic unit of electromagnetic energy.It characterizes the wave properties of electrons, as distinct from their particulate properties. The quantum theory developed by Max Planck states that the energy associated with any quantum is proportional to the frequency of the radiation, that is e (energy) = h!GKu, where !GKu is the frequency and h is a universal constant.An electron has four quantum numbers that define its properties. These are as follows: (1) The principal quantum number is a constant that can be any positive integer (n = 1, 2, 3...). It determines the principal energy level, or shell, of the electron, sometimes designated by letters such as K, L, or M, depending on the value of the principal quantum number. (2) The angular momentum constant l, also an integer, is related to n as l = 0, 1, ..., n−) 1. Here again, letter designations are often used. In s electrons, l = 0; in p electrons, l = 1; in d electrons, l = 2; and in f electrons, l = 3. (3) The magnetic quantum number, m, is an integer related to l as: m = −1, ..., −1, 0, +1, ..., +l. (4) The spin quantum number is independent of the other three and has a value of either +1/2 or −1/2, depending on the direction of rotation of the electron on its axis in the atomic frame of reference.See Orbital Theory; Electron; Photon; Radiation; Pauli Exclusion Principle.
