Question

Assertion :Alkali metals has smallest atomic size in the period. Reason: First ionization energy of nitrogen is lower than oxygen.

• 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 incorrect but Reason is correct
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is D Both Assertion and Reason are incorrect

In a period, noble gases have largest atomic size and alkali metals have second largest atomic size. In a period, on moving from left to right, the atomic size decreases.
The first ionization energy of N is higher than the first ionization energy of O. This is because the half filled 2p orbital in N $\left(1s^{2}2s^{2}2p^3\right)$ is more stable than 2p orbital in O $\left(1s^{2}2s^{2}2p^4\right)$.
Thus, the assertion and reason both are incorrect.