AP EAMCET · Chemistry · Classification of Elements and Periodicity in Properties
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 \(2 \mathrm{~s}\)-electrons.
- A Assertion and Reason both are correct statements but Reason is not correct explanation for Assertion.
- B Assertion is correct statement but Reason is wrong statement.
- C Assertion and Reason both are correct statements and Reason is correct explanation for Assertion.
- D Assertion and Reason both are wrong statements.
Answer & Solution
Correct Answer
(C) Assertion and Reason both are correct statements and Reason is correct explanation for Assertion.
Step-by-step Solution
Detailed explanation
Assertion (A) Electronic configuration of boron \((Z=5)\) is [He] \(2 s^2 2 p^1\). So, in first ionisation ( \(1 \mathrm{IE}_1\) or \(\Delta_i H_1\) ) removal will take place from unpaired \(p^1\)-electron. Whereas that of Be will be from paired \(2 s^2\)-electrons which…
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