NEETChemistryClassification of Elements and Periodicity in Properties
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The negative electron gain enthalpy of fluorine is greater than that of chlorine because fluorine is more electronegative. Reason (R): Due to the small size of the fluorine atom, there are strong interelectronic repulsions in its relatively compact 2p subshell. In the light of the above statements,
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
D. (A) is not correct but (R) is correct
Step-by-step solution
Assertion (A) is incorrect. Although fluorine is the most electronegative element, its negative electron gain enthalpy is actually less than that of chlorine. This is a well-known exception in the periodic table. Reason (R) is correct. The reason for this anomaly is that the fluorine atom is very small, and its 2p subshell is compact. When an incoming electron is added to the 2p orbitals of fluorine, it experiences strong interelectronic repulsions from the existing electrons, making the addition of the electron le