numbers are numbers assigned to all the ELECTRONS in an atom and they describe certain characteristics of the electron. It is very important to understand Quantum Numbers in order to understand the Structure of Atom. In this chapter, we’ll learn everything about Quantum Numbers. There are 4 types of quantum numbers :-Principal Quantum NumberThe Principal Quantum Number represents the principal energy level or shell in which an electron revolves around the nucleus. It is denoted by the letter n and can have any integral value except the 0 i.e. n = 1, 2, 3, 4 … ….etc. The energies of the various principal shells will follow the sequence as :K < L < M < N < O…..1 < 2 < 3 < 4 < 5……. Azimuthal Quantum NumberAzimuthal quantum number, also known as orbital quantum number determines the subshell to which an electron belongs. As a MATTER of result, the number of electronic jump increases and the number of lines at the same time.For a given value of n, it can have any integral value ranging from 0 to n – 1.For the 1ST Shell, say K, n =1,  you can have only one value i.e. l = 0For the 2nd Shell, say L, n = 2, you can have two values  i.e. l = 0 and 1For the 3RD Shell, say M, n = 3, you can have three values i.e. l = 0, 1 and 2For the 4th shells, say N, n = 4, you can have 4 values i.e. l = 0, 1, 2 and 3Magnetic Quantum NumberMagnetic Quantum Number denoted by the symbol m is what represents the orientation of atomic orbital in SPACE. The value of the Magnetic Quantum Number, m, depends on the value of l. Magnetic Quantum Number can have a total number of (2l + 1).Sublevel l mls 0 0p 1 -1, 0, +1d 2 -2, -1, 0, +1, +2f 3 -3, -2, -1, 0, +1, +2, +3Spin Quantum NumberSpin Quantum Number represents the direction of the spin of the electrons. This can either be in the direction of clockwise or even anti-clockwise. Spin Quantum Number is denoted by the symbol s. It can have about only two values i.e. +1/2 or -1/2