Order of boiling point of hydrogen halides:

The electrostatic attraction between hydrogen (covalently bonded with an electronegative atom) and another electronegative atom is known as hydrogen bonding. For example, hydrogen bonding occurs in water between H atoms (one water molecule) and O atoms (another water molecule).

Because the fluorine atom is very electronegative in comparison to other halogens, strong hydrogen bonds exist between hydrogen atoms and fluorine atoms. As a result, HF has the greatest boiling point and is present in the liquid state. The boiling point of other halogen halides is determined by van der Waal's forces. The van der Waal forces increase as the mass of halogen increases.

In HI, Van der Waals forces are stronger, while in HCl, they are lower.

Trend of the boiling point of HF, HCl, HBr, and HI.

$\mathrm{HF}>\mathrm{HI}>\mathrm{HBr}>\mathrm{HCl}$