---
title: "During the treatment of cyanide-containing wastewater, cyanate ions, \\(\\text{OCN}^{-}\\), can form. A student considers the three resonance contributors shown below. Each contributor uses 16 valence electrons and gives every atom an octet.  | Contributor | Bonding pattern | Number of lone pairs on \\(\\text{O}\\), \\(\\text{C}\\), and \\(\\text{N}\\), respectively | |————-|—————–|———————————————————————————-| | I | \\(\\text{O}-\\text{C}\\equiv\\text{N}\\) | 3, 0, 1 | | II | \\(\\text{O}=\\text{C}=\\text{N}\\) | 2, 0, 2 | | III | \\(\\text{O}\\equiv\\text{C}-\\text{N}\\) | 1, 0, 3 |  Which choice correctly identifies the contributor that makes the greatest contribution to the resonance hybrid and provides the best justification?"
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date_modified: "2026-08-19T12:40:36+00:00"
---

# During the treatment of cyanide-containing wastewater, cyanate ions, \(\text{OCN}^{-}\), can form. A student considers the three resonance contributors shown below. Each contributor uses 16 valence electrons and gives every atom an octet.

| Contributor | Bonding pattern | Number of lone pairs on \(\text{O}\), \(\text{C}\), and \(\text{N}\), respectively |
|————-|—————–|———————————————————————————-|
| I | \(\text{O}-\text{C}\equiv\text{N}\) | 3, 0, 1 |
| II | \(\text{O}=\text{C}=\text{N}\) | 2, 0, 2 |
| III | \(\text{O}\equiv\text{C}-\text{N}\) | 1, 0, 3 |

Which choice correctly identifies the contributor that makes the greatest contribution to the resonance hybrid and provides the best justification?

During the treatment of cyanide-containing wastewater, cyanate ions, \(\text{OCN}^{-}\), can form. A student considers the three resonance contributors shown below. Each contributor uses 16 valence electrons and gives every atom an octet.

| Contributor | Bonding pattern | Number of lone pairs on \(\text{O}\), \(\text{C}\), and \(\text{N}\), respectively |
|-------------|-----------------|----------------------------------------------------------------------------------|
| I | \(\text{O}-\text{C}\equiv\text{N}\) | 3, 0, 1 |
| II | \(\text{O}=\text{C}=\text{N}\) | 2, 0, 2 |
| III | \(\text{O}\equiv\text{C}-\text{N}\) | 1, 0, 3 |

Which choice correctly identifies the contributor that makes the greatest contribution to the resonance hybrid and provides the best justification?

- **A.** Contributor III, because every atom has an octet, and octet satisfaction is the only criterion needed to rank resonance contributors.
- **B.** Contributor II, because its only negative formal charge is on \(\text{N}\), and negative charge is stabilized on less electronegative atoms.
- **C.** Contributor I, because its \(\text{C}\equiv\text{N}\) bond is stronger than either double bond in contributor II, so bond strength alone determines contribution.
- **D.** Contributor I, because it avoids charge separation and places the only negative formal charge on \(\text{O}\), the more electronegative terminal atom.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119471/*