Which of the following compounds have resonance structures?

• A. ${\mathrm{NO}}_3{-}^1$ (nitrate ion)
• B. $C_2{H}_6$ (ethane)
• C. ${\mathrm{CH}}_4$ (methane)
• D. ${\mathrm{CO}}_3{-}^2$ (carbonate ion)

Answer: (D)

Verified step by step guidance

1. Step 1: Understand what resonance structures are. Resonance occurs when a molecule or ion can be represented by two or more valid Lewis structures that differ only in the placement of electrons, not the arrangement of atoms.
2. Step 2: Analyze the nitrate ion, \(NO_3^{-}\). Draw its Lewis structure and check if there are multiple ways to place the double bonds and lone pairs on oxygen atoms while keeping the overall connectivity the same. This indicates resonance.
3. Step 3: Examine ethane, \(C_2H_6\). Consider its Lewis structure and see if there are alternative valid Lewis structures differing only in electron placement. Since ethane has only single bonds and no delocalized electrons, resonance is unlikely.
4. Step 4: Look at methane, \(CH_4\). Its Lewis structure is simple with single bonds and no possibility for electron delocalization or alternative electron placements, so no resonance structures exist.
5. Step 5: Consider the carbonate ion, \(CO_3^{2-}\). Similar to nitrate, draw its Lewis structures and check for multiple valid resonance forms by shifting double bonds and lone pairs among the oxygen atoms without changing atom connectivity.