Final answer:
Molecules form hydrogen bonds due to highly polar bonds between hydrogen and electronegative atoms like O, N, or F, with hydrogen's small size enabling close interaction and strong dipole-dipole interactions.
Step-by-step explanation:
Molecules are particularly adept at forming hydrogen bonds due to the presence of highly polar bonds between hydrogen and very electronegative atoms such as oxygen (O), nitrogen (N), or fluorine (F). The substantial difference in electronegativity between hydrogen and these atoms gives the hydrogen a partial positive charge, enabling it to attract the lone pairs of electrons from similar atoms in close proximity. Additionally, because hydrogen is a small element, it allows for the bond dipoles to approach one another closely, leading to very strong dipole-dipole interactions.
These interactions are manifested in the unique properties of substances like water, which has high melting and boiling points for its size, water's solvent capabilities, high heat capacity, and expansion upon freezing. Indeed, hydrogen bonds are not only instrumental in the properties of water but also crucial for the structure and function of biological molecules such as DNA and proteins.