CBSE Class 11-science Answered

The quantum means, any physical entity (or amount)  that involves in  a reaction. 

Quantum numbers are defined as a set of four numbers with the help of which we can get a complete information about all the electrons in an atom., i.e. there location, energy, type of orbitals occupied, shape and orientation of that orbitals etc.

In simple words, the quantum numbers describe an address or full description of the electrons.

These quantum numbers are of four types - principal, azimuthal, magnetic and spin quantum numbers.

Principal quantum number (n): It defines the main shell to which an electron belongs. The values of n =1,2,3,4,........

Azimuthal quantum number (l) : It tells us the number of subshells present in the main shell and the orbital to which an electron belongs. Its value is equal to 0 to (n-1).

Magnetic quantum number (m): It informs the level of degeneracy of the orbitals. Its value is equal to -l, 0,+l.

Spin quantum number (s): It tells us whether the electron in an orbital is spinning in upward direction or downward direction. s has two values +1/2 for upward spin and -1/2 for downward spin.

Significance of Quantum numbers 

(I) It rules out the existence of definite path of the electrons and other similar particles.

(II) The effect of HUP is significant only for motion of microscopic objects and negligible for that of microscopic object.