Final answer:
Methane (CH₄) does not have resonance structures due to its stable single configuration with no delocalized electrons, whereas benzene (C₆H₆), nitrate ion (NO₃⁻), and carbonate ion (CO₃²-) all do have resonance structures because of their delocalized electrons.
Step-by-step explanation:
Molecules or ions that are described by only one structure and do not have resonance are those with no delocalized electrons and a single, unambiguous way of drawing the Lewis structure. In this case, methane (CH₄) does not have resonance structures because it has a single, stable configuration with no delocalized electrons; its four hydrogen atoms are symmetrically arranged around the central carbon atom in a tetrahedral molecular geometry.
On the other hand, the benzene molecule (C₆H₆), the nitrate ion (NO₃⁻), and the carbonate ion (CO₃²-) all have resonance structures. This is because they have delocalized electrons that can be represented by more than one valid Lewis structure, reflecting a hybrid of multiple electron distributions rather than a single static arrangement.