Final answer:
Binary acid strength increases as you move down a column of the periodic table, due to the weaker hydrogen bonds to larger atoms and increased polarity of the bond.
Step-by-step explanation:
Binary acid strength increases down a column of the periodic table. This trend is observed due to the decreasing strength of the hydrogen bond (H-A) as the size of the atom A increases. More specifically, the bond between hydrogen and a larger atom, such as iodine (I) or tellurium (Te), in a given family is weaker than the bond between hydrogen and a smaller atom, such as fluorine (F) or oxygen (O), in the same family. Consequently, the acidity of binary hydrides like HF, HCl, HBr, and HI increases from HF to HI as we move down group 17, and the acidity of binary hydrides like H₂O, H₂S, H₂Se, and H₂Te increases from H₂O to H₂Te as we move down group 16. The increasing polarity of the bond and the stability of the resulting conjugate base also contribute to the increased acidity.