Final answer:
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom is attracted to another electronegative atom from another molecule. It occurs between molecules and is an intermolecular and intramolecular attractive force. Hydrogen bonds form between hydrogen atoms and oxygen atoms in water molecules.
Step-by-step explanation:
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom is attracted to another electronegative atom from another molecule. This bond always involves a hydrogen atom and occurs between molecules. It is an intermolecular and intramolecular attractive force. For example, hydrogen bonds form between hydrogen atoms and oxygen atoms in water molecules.