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Q.
The correct sequence of electron affinity of $C , N , O$ and $F$ is
Classification of Elements and Periodicity in Properties
Solution:
Electron affinity increases from left to right in a periodic table. But electron affinity of $N$ is less than both $C $ and $O $ because $ N$ have half filled electronic configuration thus it opposes the addition of incoming electron. Thus, the order is $C > N < O < F.$