[pomalidomide]

Why does HCO₃^- have a Lewis structure where H is connected to one of the oxygen atoms and not to the central atom of carbon like I originally thought? I got very perplexed when drawing the Lewis structure for this compound because it has a valence electron of 24 but when H is connected to C, the valence electron is 25. Hope this makes sense. If not, I'll post a picture.

[AWK]

Both bicarbonate and performate anions have 24 electrons.

[Enthalpy]

Here valences help. There aren't many locations where you can put 3 oxygen atoms.

Also, many acids have hydrogen bonded with an electronegative atom like oxygen. But that's not universal.