(A) : The first ionisation energy of Be is more than that of B.
(R) : Beryllium has stable 2s² configuration in valence shell.

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(A) is true but (R) is false

Both (A) and (R) are true but (R) is not the correct explanation of (A)

Both (A) and (R) are true and (R) is the correct explanation of (A)

Both (A) and (R) are false

answer is A.

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Detailed Solution

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

Electronic configuration of Be: 1s²2s²

Electronic configuration of B: 1s²2s²2p¹

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.

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