Which substance exhibits hydrogen bonding?

• A. Ammonia
• B. Methane
• C. Oxygen gas
• D. Water

Answer: (D)

Hydrogen bonding is a strong type of intermolecular attraction that occurs when a hydrogen atom is covalently bonded to a highly electronegative atom (oxygen, nitrogen, or fluorine) and interacts with a lone pair on a neighboring electronegative atom. Water has two O–H bonds and two lone pairs on the oxygen, so each water molecule can donate hydrogen bonds from its O–H bonds and accept hydrogen bonds with its lone pairs. This enables a robust hydrogen-bond network, which is a hallmark of water's behavior and properties such as high boiling point and strong cohesion. Ammonia can form hydrogen bonds too, but they are weaker because nitrogen is less electronegative than oxygen and the bonding geometry is less optimal; methane has C–H bonds with little polarity and no lone pairs on carbon to accept hydrogen bonds; oxygen gas is nonpolar and contains no hydrogen to participate in hydrogen bonding. So water clearly exhibits hydrogen bonding.