NCl3 is indeed nitrogen trichloride, whereas AlCl3 is commonly referred to as aluminum chloride. The main reason for this difference in naming lies in the types of compounds and their components.
Firstly, NCl3 is classified as a molecular compound because it consists of non-metal elements bonded together. In molecular compounds, prefixes such as ‘tri-‘ in trichloride indicate the number of atoms present in the molecule. Thus, nitrogen trichloride denotes one nitrogen atom and three chlorine atoms.
On the other hand, AlCl3 is an ionic compound; it consists of aluminum ions and chloride ions. In ionic compounds, naming conventions are different. There’s no need for prefixes because the ratio of ions in ionic compounds is determined by the charges each ion carries. Therefore, it is simply referred to as aluminum chloride without additional naming prefixes.
In summary, the reason for the naming difference lies in the nature of the compounds: NCl3 is molecular, which requires prefixes, while AlCl3 is ionic, leading to a straightforward name.