What two properties must a donor and acceptor have in order to form hydrogen bonds?

To form hydrogen bonds, a donor must possess a hydrogen atom that is covalently bonded to a highly electronegative atom, such as nitrogen, oxygen, or fluorine. This electronegative atom attracts the shared electrons, creating a positive partial charge on the hydrogen, which makes it capable of interacting with an acceptor.

The acceptor, on the other hand, must have a lone pair of electrons available. This lone pair can interact with the partially positive hydrogen atom, resulting in the hydrogen bond. In summary, for a hydrogen bond to form, the donor must have a highly electronegative atom bonded to hydrogen, while the acceptor must have available lone pairs of electrons to facilitate the interaction between the two molecules.

The other options do not accurately capture the essential criteria required for hydrogen bond formation.