Which ion is represented by the formula N3-?

The formula N3- represents the nitride ion. In this formula, the "N" stands for nitrogen, while the "3-" indicates that there are three extra electrons associated with the atom, giving it a charge of -3. This is characteristic of the nitride ion because it is formed when a neutral nitrogen atom gains three electrons, resulting in a negatively charged ion.

In contrast, nitrogen refers to the neutral atom itself, which does not carry any charge. Ammonium is a distinct ion with the formula NH4+, and it carries a positive charge, reflecting a different structure and charge than that of the nitride ion. Nitrate, on the other hand, is represented as NO3- and consists of a nitrogen atom bonded to three oxygen atoms, also carrying a negative charge, but it is entirely different from the nitride ion. Thus, the correct identification of N3- as the nitride ion is consistent with its charge and composition.