Concept: Hydrogen bonding is an intermolecular force that occurs when a hydrogen atom bonded to a highly electronegative atom (like F, O, or N) is attracted to another electronegative atom in a different molecule. For a linear polymeric structure to form, each molecule must be able to form two hydrogen bonds in a specific orientation.

Why (B) HF is correct:

Hydrogen fluoride (HF) molecules form a zig-zag linear polymeric structure through hydrogen bonding. Each HF molecule has one hydrogen atom and one fluorine atom. The hydrogen atom of one HF molecule forms a hydrogen bond with the fluorine atom of another HF molecule, and the fluorine atom of the first HF molecule forms a hydrogen bond with the hydrogen atom of a third HF molecule. This allows for the formation of a continuous chain, $(-\mathrm{H}-\mathrm{F}\cdots \mathrm{H}-\mathrm{F}\cdots \mathrm{H}-\mathrm{F}-{)}_n$, which is a linear polymeric structure.

Option Analysis:

• A) $\mathrm{HCl}$: Although chlorine is electronegative, it is less electronegative than F, O, or N, and its larger size makes hydrogen bonding very weak or negligible in HCl. Therefore, it does not form a polymeric structure via hydrogen bonding.
• B) $\mathrm{HF}$: Forms a zig-zag linear polymeric structure due to strong hydrogen bonding between H and F atoms.
• C) ${\mathrm{NH}}_3$: Ammonia forms hydrogen bonds, but due to the presence of three hydrogen atoms and one lone pair on nitrogen, it tends to form a three-dimensional network rather than a simple linear polymeric structure.
• D) ${\mathrm{H}}_{2}O$: Water forms extensive three-dimensional networks of hydrogen bonds due to the presence of two hydrogen atoms and two lone pairs on oxygen, leading to a highly branched structure, not a linear polymer.

Correct Answer: (B)