Question 3.21
NCERT Class XI Chemistry
Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.
Solution in Detail
(video solution below this)
Point 1: O atom is small in size.
Point 2: after addition of first additional electron the electron density in the already crowded valence shell becomes so high that a second additional electron experiences a significant amount of repulsion.
Point 3: The repulsion is so high that the process becomes endothermic.
Conclusion: the second electron gain enthalpy is positive and high! [found to be +844 kJ/mol]
Video Explanation
Please watch this youtube video for a quick explanation of the solution:
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