# Quantum Numbers in Chemistry

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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.

1Western CommandChandigarh
2Eastern CommandKolkata
3Northern Command56 A.P.O
4Southern CommandPune
5Central CommandLucknow
6Army Training CommandShimla
7South Western CommandJaipur

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 :

S NoPlaceCity/State
2Akbar's TombSikandara
3Ambernath CaveKashmir
4Amber PalaceJaipur
6Bhakra DamPunjab
7Birla PlanetariumKolkata
8Black PagodaKonark (Orissa)
9BodhisattvaAjanta Caves
11Brindavan GardensMysore (Karnataka)
12Buland DarwazaFatepur Sikri
14Chenna Kesava TempleBelur
15Chilka LameNear Bhubaneswar
16Dal LakeSrinagar
17Dilwara TemplesMt. Abu
18Elephanta CavesMumbai
19Golden TempleAmirtsar
20Gol GumbazBijapur
21Hanging GardensMumbai
22Hawa Mahal (Palace of Winds)Jaipur
23Howrah BridgeKolkata
24Island PalaceUdaipur
26Jagannath TemplePuri
27Jama MasjidDelhi
28Jantar MantarDelhi
29Jog (Geresoppa) FallsMysore
30Kailasanath TemplesEllora
31Kanyakumari TemplesCape Comorin
32KhajurahoBhopal
33KonarkPuri
34Lal Bagh GardensBangalore
35Mahakaleeswar TempleUjjain
36Mahesuramurthi (Trimurti)Elephanta Caves
37Malabar HillsMumbai
38Manmandir PalaceGwalior Fort
39Marble RocksJabalpur
40Marina BeachChennai