The standard heats of formation of H2O(g), H2S(g), H2Se(g), and H2Te(g) are -241.8, -20.17, +29.7, and +99.6 kJ/mol, respectively. The enthalpies necessary to convert the elements in their standard states to one mole of gaseous atoms are 248, 277, 227, and 197 kJ/mol of atoms for O, S, Se, and Te, respectively. The enthalpy for dissociation of H2 is 436 kJ/mol. Calculate the average H-O, H-S, H-Se, and H-Te bond enthalpies, and comment on their trend.