Which of the following conditions will result in resonance in a molecule?

• A. The molecule contains only ionic bonds
• B. The presence of adjacent atoms with delocalized pi electrons or lone pairs that can be shared across multiple atoms
• C. All atoms in the molecule are connected by single sigma bonds only
• D. The molecule has no lone pairs or multiple bonds

Answer: (B)

Verified step by step guidance

1. Understand that resonance occurs when electrons, particularly pi electrons or lone pairs, can be delocalized over adjacent atoms in a molecule, creating multiple valid Lewis structures.
2. Recognize that ionic bonds involve electron transfer rather than sharing, so molecules with only ionic bonds do not exhibit resonance.
3. Note that single sigma bonds involve localized electrons between two atoms, so molecules with only single sigma bonds lack the electron delocalization needed for resonance.
4. Identify that the absence of lone pairs or multiple bonds means there are no electrons available to be delocalized, thus no resonance can occur.
5. Conclude that resonance requires the presence of adjacent atoms with delocalized pi electrons or lone pairs that can be shared across multiple atoms, allowing the electron density to be spread out over the molecule.