Question

Number of quantum numbers needed to completely define an electron in the orbit of an atom is:

• A. $3$
• B. $4$
• C. $5$
• D. depends upon the atomic number of the atom

Answer 1

The correct option is B $4$

The number of quantum numbers needed to completely define an electron in the orbit of an atom is $4$.
Thus all the four quantum numbers n, l, m and n are required. This is in accordance with Pauli's exclusion principle according to which, no two electrons in an atom can have the same set of four quantum numbers.

Hence, the correct option is $\text{B}$