Note that even highly polar but still covalent bonds e.
But you need to remember that the end products don't have broken bonds. For reaction at constant temperature of 298 K, the last term has the value 2. Energy rich substances are those that required a lot of energy to make them.
Finally, there is the matter of whether an energy is on a per molecule or per-mole basis. Let us look at a more complicated example of the formation of a molecule. Equation C-3 in Figure C-4 shows that S6 is a non-planar ing of S atoms, singly bonded. You should be able to get these numbers by remembering the few basic equations from which they are derived.