Final answer:
Hydrogen bonds require a hydrogen atom that is part of a polar covalent bond and an electronegative atom such as oxygen, nitrogen, or fluorine to act as a hydrogen bond acceptor.
Step-by-step explanation:
Formation of hydrogen bonds requires hydrogen atoms and an electronegative atom as a partner. Specifically, these bonds occur when a hydrogen atom covalently attached to one electronegative atom (such as oxygen, nitrogen, or fluorine) is attracted to a lone pair of electrons on a nearby electronegative atom. This happens because these highly electronegative atoms pull the electron density away from the hydrogen, making the hydrogen slightly positive (δ+) and able to interact with other negative partial charges (δ-).
The ability to form hydrogen bonds is important for the unique properties of substances like water. In water molecules, hydrogen atoms are covalently bonded to oxygen, creating a polar covalent bond. This polarity leads to the hydrogen atom taking on a partial positive charge and being able to form hydrogen bonds with other water molecules or electronegative atoms, giving water its high boiling point and ability to dissolve many substances.