Question

Assertion :First ionization energy of beryllium is greater than that of boron. Reason: Boron has larger size than beryllium.

• 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 C Assertion is correct but Reason is incorrect

Ionisation energy (I.E) of Be is more than B and the reason can be explained as:

Electronic configuration of Be: $1s^{2}2s^2$

Electronic configuration of B: $1s^{2}2s^{2}2p^1$

Be has stable fully filled configuration, therefore more amount of energy is required to remove an electron from Be, whereas less amount of energy is required to remove an electron from valence p-orbital in B.

Hence Assertion is correct.

Across period atomic size decreases so the reason is incorrect.

Option C is correct.