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.

Assertion (A) : Boron has a smaller first ionisation enthalpy than ber

1.	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.
Answer» Assertion and reason both are correct STATEMENTS but reason is not correct explanation for assertion. Assertion is correct statement but reason is wrong statement Assertion and reason both are correct statements and reason is correct explanation for assertion. Assertion and reason both are wrong statements. Solution :Boron has a smaller `1^(st)` ionisation enthalpy than of BERYLLIUM because INTRODUCING an electron into a 2S orbital is more than the 2p orbital. Hence, 2p electron is more shielded by the inner core of electron than the 2s electron.