bond strength

[annikaying]

What factors affect the bond strength of an acid when going down a group?

[madijohnson_4A]

As you go down a row, the bond becomes longer and therefore weaker than the bonds with elements above it. The longer bonds are due to larger nuclei, more core electrons shielding the valence electrons, and decreasing electronegativity. The longer the bond, the easier it is to break and dissociate in solution, so the stronger the acid. That's why HI, HBr, and HCl are strong acids, while HF is only a weak acid.

[VPatankar_2L]

You can compare the bond length of binary acids whose central atom varies down a group to determine which acid is stronger or weaker.