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 first ionization enthalpy of oxygen is less than that of nitrogen. Reason (R): In oxygen, the electron removal is from a doubly occupied 2p orbital, which experiences more electron-electron repulsion than the exactly half-filled 2p orbitals in nitrogen. In the light of the above statements, cho
Options
- A(A) is false but (R) is true.
- B(A) is true but (R) is false.
- CBoth (A) and (R) are true but (R) is NOT the correct explanation of (A).
- DBoth (A) and (R) are true and (R) is the correct explanation of (A).
Correct answer
D. Both (A) and (R) are true and (R) is the correct explanation of (A).
Step-by-step solution
Assertion (A) is true. The first ionization enthalpy of nitrogen is higher than that of oxygen, which is an exception to the general trend of increasing ionization enthalpy across a period. Reason (R) is true and is the correct explanation for (A). The electronic configuration of nitrogen is [ He ] 2s² 2p³ (exactly half-filled 2p subshell), which is extra stable. The electronic configuration of oxygen is [ He ] 2s² 2p⁴ . In oxygen, two electrons occupy the same 2p orbital, leading to increased electron-electron rep