Assertion :The first IE of $B e$ is greater than that of $B$ . Reason: $2 p$ -orbital is lower in energy than $2 s$ .

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Assertion is incorrect but Reason is correct

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Solution

The correct option is C Assertion is correct but Reason is incorrect
The first IE of Be (899 kJ/mol) is greater than that of B (801 kJ/mol).
B has electronic configuration $1 s^{2} 2 s^{2} 2 p^{1}$ . Be has electronic configuration $1 s^{2} 2 s^{2}$ . B has single electron in 2p orbital and Be has pair of electrons in 2s orbital. The removal of a p electron requires less energy than s-electron from same principal quantum shell. Assertion is correct but Reason is incorrect.

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Assertion :The first IE of Be is greater than that of B. Reason: 2p-orbital is lower in energy than 2s.

Assertion :The first IE of $B e$ is greater than that of $B$ . Reason: $2 p$ -orbital is lower in energy than $2 s$ .