Define quantum numbers.

Explanation

These are the numbers viz., `n, l, m_(l) , m _(a)` which give us complete information about the electron in an atom. By knowing these numbers, we can estimate the distance of an electron from the nucleus, its energy, its spin etc. These numbers are as follows:
(i) Principal quantum number (n)
(ii) Azimuthal quantum number `(l)`
(iii) Magnetic quantum number `(m_(l))`
(iv) Spin quantum number `(m_(s))`