Quantum Numbers in Chemistry
The set of four numbers which give complete information about the electron in an atom i.e., energy, orbital occupied, size, shape and orientation of that orbital and the direction of electron spin.
(a) Principal Quantum Number (n)
It gives the major energy level to which the electron belongs.
Thus, n = 1, 2, 3,… etc depending upon whether the electron belongs to first, second, third etc. energy levels For the first energy level (K – shell) n = 1, for second (M – shell) n = 2, etc.
(b) Azimuthal (or) Subsidiary (or) Angular Momentum Quantum Number (I)
It gives the energy level of subshells. It gives the following information :
- Number of subshells present within a main shell.
- Shapes of subshells.
- Contribution of energy due to angular momentum towards the total energy of the electron.
- For a given value of n, l can have values from 0 to (n – 1).
- For n = 1(K), l = 0 i.e. one subshell (s)
- n = 2 (L), I = 0, 1 i.e., two subshells (s, p)
- n = 3 (M), l = 0, 1, 2 i.e., three subshells (s, p, d)
- n = 4 (N), I = 0, 1, 2, 3 i.e., four subshells (s, p, d, f)
Order of energies : s < p < d < f
It was proposed by Sommerfeld.
(c) Magnetic Quantum Number (m)
It tells the number of orditals present within the same subshell.
For a given value of I, m can have values from -l to +l including 0, making a total of (2l + 1) values.
These quantum number also give the orientation of the orbital.
The number of orbital in a shell with principal quantum number n is equal to n²
The orbitals having same energy level are called degenerate orbitals.
|3||Northern Command||56 A.P.O|
|6||Army Training Command||Shimla|
|7||South Western Command||Jaipur|
It was given by Lande to explain Zeeman and Stark effects.
(d) Spin Quantum Number (s)
This arises due to the spinning of the electron about its own axis.
It can be clockwise represented by +1 / 2 or or anticlockwise represented by -1/2.
This is the only quantum number that has non – integral values. It was introduced by Uhlenbeck and Goudsmet.
Distribution of Electrons in Quantum Levels :
|8||Black Pagoda||Konark (Orissa)|
|11||Brindavan Gardens||Mysore (Karnataka)|
|12||Buland Darwaza||Fatepur Sikri|
|14||Chenna Kesava Temple||Belur|
|15||Chilka Lame||Near Bhubaneswar|
|17||Dilwara Temples||Mt. Abu|
|22||Hawa Mahal (Palace of Winds)||Jaipur|
|29||Jog (Geresoppa) Falls||Mysore|
|31||Kanyakumari Temples||Cape Comorin|
|34||Lal Bagh Gardens||Bangalore|
|36||Mahesuramurthi (Trimurti)||Elephanta Caves|
|38||Manmandir Palace||Gwalior Fort|
|43||Panch Mahal||Fatepur Sikri|
|44||Tower of Fame||Chittorgarh|