Advanced Placement (AP) Chemistry Practice Exam

Which of the following elements is most commonly associated with strong hydrogen bonding interactions?

1. Carbon

2. Fluorine

3. Sodium

4. Phosphorus

The correct answer is: Fluorine

Fluorine is most commonly associated with strong hydrogen bonding interactions due to its high electronegativity and small atomic size. When fluorine is part of a compound, it creates a significant dipole moment, which allows it to strongly attract hydrogen atoms that are covalently bonded to highly electronegative elements such as nitrogen, oxygen, or itself. The strength of hydrogen bonds formed by fluorine compared to other elements is particularly pronounced because these bonds involve the close approach of positively charged hydrogen nuclei to the lone pairs of electrons on the fluorine atom. Furthermore, fluorine's position at the top of the periodic table means that it can form very strong hydrogen bonds, which play a critical role in determining the physical properties of substances, such as water's high boiling point compared to similar-sized molecules. The other options do not have the same degree of involvement in strong hydrogen bonding interactions; for example, carbon mainly forms covalent bonds without significant hydrogen bonding capability, while sodium is a metal that forms ionic bonds, and phosphorus does have some capacity for bonding but does not exhibit hydrogen bonding to the same extent as fluorine.