Question

Which of the following has highest electron affinity?

• A. F
• B. Cl
• C. N
• D. O

Answer 1

The correct option is B

Cl

Here, one of the most important things to keep in our mind is that Group 17 elements have maximum electron gain enthalpy because if we add one electron to group 17 elements, they achieve noble gas configuration.

Therefore, F & Cl will have high electron affinity than N and O.

Now, when we have to compare between F & Cl.

As we know,

Fluorine, though higher than chlorine in the periodic table, has a very small atomic size. This makes the fluoride anion so formed unstable (highly reactive) due to a very high charge/mass ratio. Also, fluorine has no d-orbitals, which limits its atomic size. As a result, fluorine has an electron affinity less than that of chlorine.