Why is the bond length of HI longer than that of HCl?

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SUMMARY

The bond length of hydrogen iodide (HI) is longer than that of hydrogen chloride (HCl) due to the larger atomic radius of iodine compared to chlorine. This larger radius results in a weaker electrostatic attraction between the hydrogen and iodine atoms, as the H-I bond is less polar than the H-Cl bond due to iodine's lower electronegativity. Consequently, the increased distance between the atoms in HI leads to a longer bond length, contrary to initial assumptions that larger atomic radii would result in shorter bond lengths.

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Why did you think that the larger atomic radius of iodine makes the bond length of HI smaller? Correct me if I'm wrong but it's pretty common sense that the larger the atomic radius, the longer the bond length. Besides, due to the smaller electronegativity of iodine, H-I bond is not as polar as H-Cl and therefore less electrostatic attraction due to partial charges is experienced by H and I, thus they are further apart, increasing the bond length.
 
dorebase2006 said:
Why did you think that the larger atomic radius of iodine makes the bond length of HI smaller? Correct me if I'm wrong but it's pretty common sense that the larger the atomic radius, the longer the bond length. Besides, due to the smaller electronegativity of iodine, H-I bond is not as polar as H-Cl and therefore less electrostatic attraction due to partial charges is experienced by H and I, thus they are further apart, increasing the bond length.

I was exploring other avenues of thought ;)

Thanks for the explanation.
 

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