Assertion (A) : The first ionization energy of Be is greater than that of B.
Reason (R) : $2 P$ Electrons are more loosely held than $2 S$ electrons.

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Both A and R are correct and R is the correct explanation of A.

A is correct, R is incorrect.

A is incorrect, R is correct.

Both A and R are correct but R is not the correct explanation of A.

answer is A.

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Detailed Solution

Assertion: It is fact that first ionization energy of Be is greater than that of B because the electron has to be removed from the more stable $2 S^{2}$ half –filled orbital than the electron from $2 p^{1}$ incompletely filled orbital of B.

Reason: R is correct ,and the correct explanation of A. Actually the ionisation energy depends on the penetration power of the orbitals , the order of penetration power of orbitals is $s > p > d > f$ Therefore $2 p$ Electrons are more loosely held than $2 s$ electrons.

$2 p$ Electrons are more loosely held than $2 s$ 2S electrons.

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