Why do group 16 hydrides become more acidic farther down the periodic table?

In group 16 of the periodic table, the acidity of hydrides increases as you move down the group—from water ($H_{2}O$) to hydrogen sulfide ($H_{2}S$), hydrogen selenide ($H_{2}Se$), and hydrogen telluride ($H_{2}Te$).12

This trend is primarily driven by the decreasing bond strength of the element-hydrogen bond as the atomic size of the central element increases. Because the bond becomes weaker farther down the group, it requires less energy to break, making it easier for the molecule to donate a hydrogen ion ($H^{+}$) in aqueous solution. While factors such as electronegativity and ionic solvation energy also play roles in acid-base behavior, the reduction in bond strength is the most significant factor in this specific periodic trend.12