Acids HF, HCl, HBr and HI

The strengh of an acid depends on the strength and polarity of the bond. A weaker bond and a more polarised bond, yields a stronger acid. Electrostatic potential maps shows the bond polarity. The red is the parts is electron rich and slightly negatively charged. The dark blue is electron poor areas and slightly positively charged. The green part is neutral. So the hydrogens are electron poor and the halides are electron rich. HF has the most polarised bond and the amount the bond is polarised decreases as we go down the group. The bond strengh plays a larger role than the polarity of the bond in this series. HF has the lowest acid strength of these acids due to the highest bond strength HF has. HF has the highest bond strength due to the smallest size of the fluorine in comparison to the other acids in the series. The size of the halides increases down the group and the bond strength decreases down the group. HI has the largest halide iodide, the weakest bond and thus it is the strongest acid in this series.