Quantum Numbers - Practice Questions & MCQ

Quantum numbers:

They are the set of four numbers which explain the state of electron i.e., location, energy, type of orbital, orientation of orbital, etc. in an atom. Various quantum numbers are as follows:

1. Principal quantum number(n)

2. Azimuthal quantum number(l)

3. Magnetic quantum number(m)

4. Spin quantum number(s)

Principal quantum number(n):

It represents the principal shell of an atom. It can have integral values except zero like 1,2,3,.... Also denoted as K,L,M,.....etc.

Maximum number of electrons in a principal shell can be 2n2 where n is principal quantum number.

This quantum number gives information about :

• Distance of electron from nucleus i.e., size of electron cloud.
• Energy of electron in any shell

Where, Z is atomic number and n is principal quantum number.

Azimuthal quantum number(l):

Azimuthal quantum number represents the subshell or subenergy shell in an atom.

l has values from 0 to (n-1).

For eg: for n=2 ; l= 0, 1

Subshell notation for 0, 1 is s and p.

No. of electrons [2(2l+1)]: for s subshell = 2; for p subshell = 6.

Magnetic quantum number(m):

It represents the number of orbitals present in a subshell.

m has values ranging from -l to +l including zero.

For eg: for ‘s’ subshell :

1. Value of l is 0

2. m has value=0

For ‘p’ subshell :

1. Value of l is 1

2. m has value= -1, 0, +1

Spin quantum number(s):

Electron in an orbital can spin either clockwise or anticlockwise.

Thus, an electron can have only two possible values of this quantum number, either   or respectively.