Question

Which halogen forms the strongest bond with hydrogen to form `HX`?

Answer 1

Which atom forms the strongest bond with hydrogen; which acid is the weakest? Clearly, it is fluorine.

Explanation:

The strongest `H-X` bond is definitely between hydrogen and fluorine. Fluorine is a first row element; it makes sense that there is better overlap between fluorine/hydrogen orbitals, than between chlorine/hydrogen orbitals. The strength of the `H-F` bond is well illustrated by the acidity of the hydrohalic acids. `H-Cl`, and `H-Br` undergo almost complete dissociation in water; they are strong acids. `H-F` is considered to be a weak water acid in that the smaller fluorine atom tenaciously binds to the proton.

As a physical scientist you should look up the numbers, and look at the `pK_a`'s of the hydrohalic acids.