Question

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

(i) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(ii) Assertion is correct statement but reason is wrong statement.

(iii) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(iv) Assertion and reason both are wrong statements.

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Answer 1

Assertion : Boron has a smaller first ionisation enthalpy than beryllium.

Reason : The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons.

Solution : atomic no of B = 5

Electronic configuration of B = 1s², 2s², 2p¹

atomic no of Be = 4

Electronic configuration of Be = 1s², 2s²

Here it is clear that, beryllium outermost orbit is completely filled so higher energy is required to eject electron from outermost shell. Therefore, Boron has a smaller Ionisation enthalpy than beryllium. Assertion is correct.

reason, The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons, is correct also explanation of assertion.

so the correct option is (iii)

Answer 2

Answer:

OPTION iii

Explanation: