Which of these species have resonance or isomers

Which of these species have resonance or isomers? CH4, CH2Cl2, CH4O, H2O, H3O+, HF, NH3, H2O2, N2, P4

The correct answer and explanation is:

Correct Answer:

Among the given species, H₂O₂ (hydrogen peroxide) and N₂ (nitrogen gas) exhibit resonance or have isomers.

Explanation (300 words):

To determine if a molecule has resonance or isomers, it is essential to understand what these terms mean. Resonance refers to the situation where more than one valid Lewis structure can be drawn for a molecule, involving the delocalization of electrons. Isomers, on the other hand, are compounds that have the same molecular formula but different structures or arrangements of atoms.

Let us evaluate each species:

1. CH₄ (methane) – It has a simple tetrahedral structure with no multiple bonds or lone pairs capable of delocalization. No resonance or isomers.
2. CH₂Cl₂ (dichloromethane) – It has a tetrahedral structure and no resonance. Although the chlorine atoms can be arranged differently, this does not produce true structural isomers due to free rotation and molecular symmetry.
3. CH₄O (methanol) – It does not have resonance. While different representations exist (like methyl alcohol and a hypothetical structure like CH₃–OH or CH₂–H–OH), they are not actual isomers under normal conditions.
4. H₂O (water) – Has a bent structure with no resonance or isomers.
5. H₃O⁺ (hydronium ion) – It has a trigonal pyramidal shape. No resonance because there are no delocalized pi bonds.
6. HF (hydrogen fluoride) – A simple diatomic molecule with a single bond. No resonance or isomers.
7. NH₃ (ammonia) – Trigonal pyramidal shape with no resonance or isomers.
8. H₂O₂ (hydrogen peroxide) – Has isomers (conformational) due to rotation around the oxygen–oxygen single bond. The molecule can exist in different spatial arrangements.
9. N₂ (nitrogen gas) – Has resonance. Although the main structure is a triple bond between two nitrogen atoms, resonance can describe the delocalization of electrons among equivalent structures.
10. P₄ (white phosphorus) – It has a unique tetrahedral shape. No resonance, and all atoms are chemically equivalent, so no isomers in this form.

Thus, only H₂O₂ and N₂ exhibit resonance or have isomers.