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 O is lower than that of N and F. Reason R : The loss of an electron from O leads to stable half-filled p orbital. In light of the above statements, choose the most appropriate answer from the options given below:
B. Both A and R are correct and R is the correct explanation of A .
The electronic configuration of N is 1s^2 2s^2 2p^3. The electronic configuration of O is 1s^2 2s^2 2p^4. The electronic configuration of F is 1s^2 2s^2 2p^5. Generally, the first ionization enthalpy increases across a period due to an increase in effective nuclear charge. Therefore, the ionization enthalpy of F is higher than that of O . However, N has a stable half-filled 2p^3 configuration, which makes it difficult to remove an electron, resulting in a higher ionization enthalpy than O . For O , the loss of one electron results in the stable half-filled 2p^3 configuration ( O ^+ is 1s^2 2s^2 2p^3). This extra stability of the resulting ion makes the removal of the first electron from O easier compared to N . Hence, the first ionization enthalpy of O is lower than that of both N and F . Assertion A is correct. Reason R is also correct and provides the correct explanation for Assertion A. Answer: Both A and R are correct and R is the correct explanation of A .
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