Question

The acidic character of hydrides of group 16 elements increases from ${\mathrm{H}}_2\mathrm{O}$ to ${\mathrm{H}}_2\mathrm{Te}$. Why?

Answer 1

• Compounds of hydrogen with less electronegative elements are known as hydrides.
• If the bond length between the element and hydrogen is long, it means that the bond is not strong. Therefore, the bond can be broken easily.
• Down the group, the $\mathrm{H}-\mathrm{E}$ bond length between the element and hydrogen increases and thus the enthalpy of the $\mathrm{H}-\mathrm{E}$ bond decreases down the group.
• The acidic character of hydrides of group 16 elements increases from ${\mathrm{H}}_2\mathrm{O}$ to ${\mathrm{H}}_2\mathrm{Te}$ because the bond dissociation enthalpy of the $\mathrm{H}-\mathrm{E}$ bond decreases down the group.