For which of these molecules does the best Lewis structure have two or more equivalent resonance structures? A. SCN - B. CNO - C. HCO2 - D. CO2 E. N3-

C. HCO₂⁻

Explanation:

The equivalent resonance structures is a way to stabilize the charges and the sharing of the electrons in the compounds. The isolated electrons and the shared are relocated, and more then one structure is permitted. But, if there is a huge difference in electronegativity, one structure is considered more correct. So, let's analyze:

A.

[S = C = N]⁻ ⇔ [S - C ≡ N]⁻

Because N has huge electronegativity, the second structure is more presented, so, they are not equivalent.

B.

[O = C = N]⁻ ⇔ [O - C ≡ N]⁻

Nitrogen is more electronegative than oxygen, so the second structure is more present, then they are not equivalent.

C.

[O = C - O]⁻ ⇔ [O - C = O]⁻

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H H

There is the same atom, so the structures are equivalents.

D.

O = C = O

There are no resonance structures

E.

[N = N - N]⁻

The change in the structure will result in the same compound, only seen by another perspective, so there are no resonance structures.