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Question: Answered & Verified by Expert
Assertion : Ionisation potential of B (atomic no.5) is less than Be (atomic no. 4).
Reason : The first electron released from Be is of $p$-orbital but that from B is of $s$-orbital.
ChemistryStructure of AtomAIIMSAIIMS 2001
Options:
  • A If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
  • B If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
  • C If Assertion is true but Reason is false.
  • D If Assertion is false but Reason is true.
Solution:
2811 Upvotes Verified Answer
The correct answer is: If Assertion is true but Reason is false.
Electronic configuration of berylium and boron is given as :
$$
\begin{aligned}
& \operatorname{Be}(Z=4): 1 s^2, 2 s^2 \\
& \operatorname{B}(Z=5): 1 s^2, 2 s^2, 2 p^1
\end{aligned}
$$
Ionisation potential of $\mathrm{Be}$ is greater than that of boron as first electron released from $B e$ is from $s$-orbital while it is from $p$-orbital in boron.

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