Question

Assertion :$I.E_1$ of B is slightly less than that of $Be$. Reason: $2s$ electron is less penetrated than $2p$ towards nucleus.

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

Answer 1

The correct option is C Assertion is true statement but Reason is false

• The first ionisation energy of Boron is less than that of Beryllium this is due to the 2s orbital being totally filled in beryllium, whereas boron has one electron in a 2p orbital as well, and the 2s orbital is shielded much more than the 2p orbital, which gives boron a lower ionisation energy (as its valence electron is easier to remove).
  
• Hence Boron is having less I.E-1 than Beryllium.
• Hence,option C is correct answer.