Assertion (A) Boron has a smaller first ionisation enthalpy than beryllium. Reason (R) The penetration of a (2 s )-electron to the nucleus is more than the (2 p )-electron hence, (2 p )-electron is more shielded by the inner core of electro

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Assertion (A) Boron has a smaller first ionisation enthalpy than beryllium. Reason (R) The penetration of a (2 s )-electron to the nucleus is more than the (2 p )-electron hence, (2 p )-electron is more shielded by the inner core of electrons than (2 ~s )-electrons.

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Correct answer: C. Assertion and Reason both are correct statements and Reason is correct explanation for Assertion.

Assertion (A) Electronic configuration of boron ((Z=5) ) is [He] (2 s^2 2 p^1 ). So, in first ionisation ( (1 IE ₁ ) or ( _i H₁ ) ) removal will take place from unpaired (p^1 )-electron. Whereas that of Be will be from paired (2 s^2 )-electrons which requires more energy. Electronic configuration of ( Be (Z=4):[ He ] 2 s^2 ) So, the Assertion is a correct statement. Reason (R) (s )-orbital is being symmetrical in shape (spherical), it shields nuclear force (nuclear charge) strongly. So, (2 p^1 )-electron of (B ) is

Assertion (A) Boron has a smaller first ionisation enthalpy than beryllium. Reason (R) The penetration of a (2 s )-electron to the nucleus is more than the (2 p )-electron hence, (2 p )-electron is more shielded by the inner core of electrons than (2 ~s )-electrons.

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