Quantum numbers are defined as a set of four numbers with the help of which we can get complete information about all the electrons in an atom. Thus with the help of these numbers we can get the information about the energy, location, type of orbital occupied, shape of that orbital etc. Mainly there are four types of quantum numbers. They are:

☛ a. Principal Quantum Number: It is denoted by n. It tells us about the energy level or shell in which the electron is present. The value of n can be 1,2,3,4…….etc. but it cannot be zero. It gives us the information about the average distance of electrons from the nucleus, determines the energy of electron in hydrogen atom and hydrogen like atoms. It also gives us the information about the maximum number of electrons that a shell can have by using the formula 2n2.

☛ b. Azimuthal Quantum Number: It is denoted by l. Through this quantum number we get to know the number of sub-shells present in the main shell. It also gives information about the shapes of various shells present within the same principal shell and also about the relative energies associated with these sub-shells.

☛ c. Magnetic Quantum Number: It is denoted by m. This quantum number explains us that when a source producing spectral lines are placed in a magnetic field, then each spectral line splits up into number of lines. This is also known as Zeeman Effect.

☛ d. Spin Quantum Number: The electron not only spins around the nucleus but also about its own axis. The direction of electron spin is clockwise or anti-clockwise. This quantum number helps to explain the magnetic properties of the substance.