Q.Match the items given in Column I with examples given in Column II.
Column I

The key idea is classifying chemical species by bonding and structural features — each entry in Column I describes a distinct bonding or electronic phenomenon.

• (i) Hydrogen bond — occurs between molecules where H is bonded to a highly electronegative atom. HF exhibits strong hydrogen bonding.
• (ii) Resonance — delocalisation of electrons within a molecule. Ozone ($O_3$) has two equivalent resonance structures. …

Let’s think about what each term in Column I really means — not just a definition, but the physical picture behind it.

Hydrogen bond is a special type of intermolecular attraction that occurs when hydrogen is bonded to a highly electronegative atom (like F, O, or N) and is attracted to a lone pair on another electronegative atom. It’s not a full covalent bond, but a strong dipole-dipole interaction.

Resonance describes a situation where a single Lewis structure cannot fully represent a molecule; the actual structure is a hybrid of multiple contributing structures, with delocalized electrons. This often stabilizes the molecule.

Ionic solid is a crystalline solid held together by electrostatic forces between oppositely charged ions. It typically forms between a metal and a non-metal, with a large electronegativity difference.

Covalent solid (also called a network solid) is a solid where atoms are bonded together in a continuous network of covalent bonds. It’s hard, has a high melting point, and does not consist of discrete molecules.

Now let’s match each one step by step.

1. Hydrogen bond — Look at the options: (c) H₂ and (d) HF are the only ones with hydrogen. H₂ has no electronegative atom to create a hydrogen bond; it’s just a nonpolar covalent molecule. HF, however, has hydrogen bonded to fluorine — the most electronegative element. HF molecules form strong hydrogen bonds with each other. So (i) matches with (d) HF.

2. Resonance — Which of these molecules cannot be described by a single Lewis structure? O₃ (ozone) is a classic example. Its two O–O bonds are identical in length, intermediate between a single and double bond, because the electrons are delocalized over the three atoms. C (diamond) has no resonance; LiF is ionic; H₂ and HF are simple covalent molecules with one valid structure. So (ii) matches with (e) O₃.

3. Ionic solid — LiF is lithium fluoride. Lithium is a metal, fluorine is a non-metal. The electronegativity difference is huge, so electrons transfer completely, forming Li⁺ and F⁻ ions. These ions arrange in a crystal lattice held by electrostatic forces. That’s the definition of an ionic solid. So (iii) matches with (b) LiF. …