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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, but the second ionization enthalpy of oxygen is greater than that of nitrogen. Reason (R): The atomic radius of oxygen is smaller than that of nitrogen. In the light of the above statements, choose the most appropriate answer fr

Options

  1. ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
  2. BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
  3. CAssertion (A) is true but Reason (R) is false.
  4. DAssertion (A) is false but Reason (R) is true.

Correct answer

B. Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).

Step-by-step solution

Assertion (A) is true: The first ionization enthalpy of nitrogen ( 2s^2 2p^3 ) is higher than that of oxygen ( 2s^2 2p^4 ) due to the extra stability of the exactly half-filled 2p subshell in nitrogen. However, after removing one electron, the oxygen cation ( O ^+ ) acquires a stable half-filled 2p^3 configuration, while the nitrogen cation ( N ^+ ) has a 2p^2 configuration. Thus, removing a second electron is harder for oxygen, making its second ionization enthalpy greater than that of nitrogen. Reason (R) is true

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