Three isomers having the formula $\mathrm{N}_{2} \mathrm{CO}$ are known: ONCN (nitrosyl cyanide), ONNC (nitrosyl isocyanide), and NOCN (isonitrosyl cyanide). Draw the most important resonance structures of these isomers, and determine the formal charges. Which isomer do you predict to be the most stable (lowest energy) form? (See G. Maier, H. P. Reinsenauer, J. Eckwert, M. Naumann, M. De Marco, Angew. Chem., Int. Ed. $1997,36,1707 .