Which diatomic molecule contains the strongest bond?

$\mathrm{H}-\mathrm{F} >\mathrm{H}-\mathrm{Cl}$

$2s-2p$  $2s-3p\text{ overlap }$

There is an impact that is even more significant than electronegativity. The outer valence electrons get further separated from the nucleus as we/you move along the group because the shell number (n) rises.The ability of an element to "tightly" hold onto hydrogen decreases with size. For the periodic table, the pattern is that the stronger the acid, the more electronegative the atom, but that is only because throughout a row, the size of the elements scarcely changes. HF therefore has the oddest bond.