Which of the halogens has the largest negative `Delta_(eg)H`?

Options

A. `I`
B. `Br`
C. `C1`
D. `F`

Answer

C

Explanation

The correct order of decreasing negative `Delta_(eg)H` is
`CIgt Fgt Brgt Igt At`
In fact, `CI` has the larger negative `Delta_(eg)H` in the periodic table. Unexpectedly low negative `Delta_(eg)H` of `F` is related to its relatively small size which results in large `e^(-)-e^(-)` repulsion.