Which of the following is the correct formula for the cyanide ion?

The cyanide ion is represented by the formula CN(-). This formula indicates that the ion consists of one carbon atom (C) bonded to one nitrogen atom (N), and it carries a negative charge. The negative charge typically results from the carbon atom having a complete octet while the nitrogen atom possesses an unshared pair of electrons, making the overall entity an anion.

In the context of the incorrect options, SCN(-) corresponds to the thiocyanate ion, where sulfur is bonded to carbon and nitrogen, which is not the definition of cyanide. OCN(-) represents the oxalate ion (or cyanate ion), which includes an oxygen atom and changes the structural arrangement compared to cyanide. Lastly, NO2(-) denotes the nitrite ion, entirely unrelated to the composition of the cyanide ion since it involves nitrogen and oxygen only.

Therefore, the formula CN(-) is correct, as it accurately depicts the cyanide ion’s structure and charge.