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  • 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.

In the following questions, a statement of Assertion (A) followed by a statement of the reason (R) is given. Choose the correct option out of the choices given below each 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.

  1. Assertion and reason both are correct statements, but reason is not correct explanation for assertion.
  2. Assertion is correct statement, but reason is wrong statement.
  3. Assertion and reason both are correct statements and reason is correct explanation for the assertion.
  4. Assertion and reason both are wrong statements.

Answers (1)

The answer is the option (iii) Assertion and reason both are correct statements and reason is correct explanation for the assertion.

Explanation: During ionisation, the electron removed in case of beryllium is from the s-orbital and the electron removed from the boron atom is from the p-orbital, and the penetration of 2s electron to the nucleus is more than that of 2p electron hence 2p electron of boron is more shielded from the nucleus than the 2s electron.

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