Which of the following species contains a delocalized pi (π) bond?

• A. O3 (ozone)
• B. CO2 (carbon dioxide)
• C. H2O (water)
• D. CH4 (methane)

Answer: (A)

Verified step by step guidance

1. Understand what a delocalized pi (π) bond means: it is a pi bond where the electrons are spread over three or more atoms rather than localized between two atoms. This usually occurs in molecules with resonance structures.
2. Examine each species for the presence of pi bonds and resonance. Start with O3 (ozone): O3 has resonance structures where the pi electrons are shared over the three oxygen atoms, indicating delocalization.
3. Look at CO2 (carbon dioxide): CO2 has two double bonds between carbon and oxygen, but these pi bonds are localized between the carbon and each oxygen atom, with no resonance delocalization over multiple atoms.
4. Consider H2O (water) and CH4 (methane): both molecules have only single bonds (sigma bonds) and no pi bonds, so they cannot have delocalized pi electrons.
5. Conclude that among the given species, only O3 contains delocalized pi bonds due to its resonance structures spreading the pi electrons over multiple atoms.