HCl, HBr , HI which one is more acidic and why?

 HI is the most acidic one of them followed by HBr and last HCl.

But why?

As the more acidic compound the the one tend to dissociate more and release hydrogen ions in the media, as dissociation occurs the anion part in emerging in case of HCl, chloride ion is formed and so one Bromide and iodide.

As you already know that the charge on the atom makes it less stable than the neutral atom.

now if you took a break and overlooked the periodic table, and focused on group 7A(the halogens), you will see from top to bottom Cl comes above Br and the followed by I. And the atoms are growing bigger in size as deciding down the column then the size ranking is as follow; the iodide ion the the biggest followed by bromide and the chloride is the smallest. Now the bigger atoms has the ability to distribute the negative charge in a larger space than the smaller atoms, so the iodide ion can distribute the negative charge in a larger area more the bromide ion, and bromide can distribute the negative charge more than chloride can do, so the iodide ion is the most stable ion of then all, followed by bromide then chloride. Since iodide is the most stable it then tend to dissociate more often than then other so tend HI tend to release H ions more than HBr O HCl so HI is the most acidic.

and the same logic is true for HBr superiority over HCl.

In case of HF it is NOT considered acid at all Fluoride ion is too small to handle the negative charge so it will NOT dissociate at the first place. 

 

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