Draw dot diagrams for all resonance forms of the \(\mathrm{NCO}^{-}\) ion.

To begin, determine the valence electrons for each atom in the \(\mathrm{NCO}^{-}\) ion: - Nitrogen (N) has 5 valence electrons - Carbon (C) has 4 valence electrons - Oxygen (O) has 6 valence electrons - The extra negative charge adds 1 more valence electron The total number of valence electrons in the \(\mathrm{NCO}^{-}\) ion is 5 + 4 + 6 + 1 = 16 electrons. Place the least electronegative atom (C) in the center and draw single bonds between the central atom and the outer atoms. Then, distribute the remaining electrons as lone pairs around the atoms. Here's the initial Lewis structure: \(N=C-O\) The octet rule is satisfied for all three atoms: Nitrogen has 2 lone pairs (totaling 4 electrons) and shares 4 electrons in a double bond with Carbon, Carbon has no lone pairs but shares all its valence electrons in bonds with Oxygen and Nitrogen, Oxygen has 3 lone pairs (a total of 6 electrons) and shares 2 electrons in a single bond with Carbon.

Analyze the initial Lewis structure to see if there are other ways to arrange the double and single bonds by relocating the electrons. In this case, we can change the location of the double bond to be between Carbon and Oxygen, while the single bond is between Nitrogen and Carbon. The atoms will maintain their octet configuration. Here is another possible resonance structure for the \(\mathrm{NCO}^{-}\) ion: \(N-C=N\) Now, the Nitrogen has 3 lone pairs (totaling 6 electrons) and shares 2 electrons in a single bond with Carbon, Carbon has no lone pairs, and shares all its valence electrons in bonds with Nitrogen and Oxygen, Oxygen has 2 lone pairs (totaling 4 electrons) and shares 4 electrons in a double bond with Carbon.

Display the two resonance structures and use a double-headed arrow to indicate that they are resonance forms of each other: \(N=C-O ↔ N-C=N\) These two resonance structures represent the different possible ways electrons can be arranged in the \(\mathrm{NCO}^{-}\) ion, which contributes to its overall stability.