Question

How would you expect the extent of overlap of atomic orbitals to vary in the series `"IF"`, `"ICI"`, `"IBr"`, and `"I"_2`?

Answer 1

Well, for these interhalogens, you would expect that the order of overlap between atomic orbitals DECREASES down the group........

Explanation:

A priori, we would expect BETTER overlap, and stronger bonding, when the heteroatom is smaller (caution, the `F-F` is disproportionately weak, and this is attributed to lone pair interaction between the fluorine atoms).

And thus, in terms of bonding interaction:

`I-F>I-Cl>IBr>I_2`.

And how could we assess this? Well, one way could be the interhalogen bond strength.........And I would consult your inorganic chemistry text for actual values.