A hydrogen bond is a weak attraction between a hydrogen atom and another atom.

• A. Covalent bond
• B. Weak attraction between a hydrogen atom and another atom
• C. Ionic bond
• D. Metallic bond

Answer: (B)

Hydrogen bonds are a type of weak intermolecular attraction that occurs when a hydrogen atom, covalently bonded to a highly electronegative atom, is attracted to a lone pair on another electronegative atom nearby. This is exactly what the statement describes—a weak attraction between a hydrogen atom and another atom.

This isn’t a covalent bond, where electrons are shared between atoms within a molecule; nor an ionic bond, which involves transfer of electrons and electrostatic attraction between charged ions; nor a metallic bond, which involves a lattice of positively charged atoms with a sea of delocalized electrons. Hydrogen bonds sit between these stronger bonds and other noncovalent interactions, and while individually weaker than covalent or ionic bonds, they collectively have powerful effects, such as giving water its unusual properties and stabilizing structures in DNA and proteins.