Question

Assertion :An orbital cannot have more than two electrons and they must have opposite spins. Reason: No two electrons in an atom can have same set of all the four quantum numbers as per Pauli's exclusion principle.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

The Pauli exclusion principle is the quantum mechanical principle which states that two or more identical fermions (particles with half-integer spin) cannot occupy the same quantum state within a quantum system simultaneously.

In the case of electrons in atoms, it can be stated as follows: it is impossible for two electrons of a poly-electron atom to have the same values of the four quantum numbers: $n$, the principal quantum number, $l$, the angular momentum quantum number, $m$, the magnetic quantum number, and $s$, the spin quantum number.

For example, if two electrons reside in the same orbital, and if their $n$, $l$, and $m$ values are the same, then their $s$ must be different, and thus the electrons must have opposite half-integer spin projections of 1/2 and −1/2