Why do we call Ca3N2 calcium nitride instead of tricalcium dinitride?
There’s only one way a nitride of calcium can form.

You can’t have tricalcium mononitride. So you already know that if you say calcium nitride there are three calcium ions and two nitrogen ions. To say tricalcium dinitride does not add any information.

We compare this to carbon and oxygen. You say carbon dioxide because it gives you information. You can have carbon dioxide or carbon monoxide. Carbon oxide would not provide enough information, monocarbon dioxide provides information we already know.

What is the full name of Ca3N2?
Calcium nitride is a solid brown nitride powder and an inorganic compound with constituent elements calcium and nitrogen and represented. Calcium nitride is with the chemical formula Ca3N2. It has various isomorphs forms, and α-calcium nitride is more commonly encountered. Calcium nitride powder possesses the characteristics of high purity and uniform particle size distribution. Calcium nitride is a red-brown, crystalline solid made up of calcium and nitrogen.

1. Calcium nitride Ca3N2 powder preparation
Ca3N2 is formed along with the oxide, CaO, when calcium burns in the air. Heat the distilled fibrous metallic calcium to 450℃ in a purified nitrogen stream, and then metallic calcium is nitrided to calcium nitride after 3 to 4 hours.

Depending on the temperature of preparation, the obtained calcium nitride is black when 350℃, milky white when 350 to 1150℃, or golden yellow when 1150℃ or higher. It is easy to identify the calcium nitride formed since it can react with moisture or water and produce calcium hydroxide and ammonia.
Physical and chemical properties of Ca3N2 powder
Calcium nitride is a brown crystal and an ionic compound with a density of 2.63 g/cm3 and a melting point of 1195℃. Its CAS number is 12013-82-0, and the molar mass is 148.248 g·mol−1. It is a black, golden yellow or milky white hexagonal crystal under different conditions. Its crystal structure is cubic. Besides, α-calcium nitride will turn into β-calcium nitride at 700℃. α-calcium nitride adopts an anti-bixbyite structure, similar to MnO, but the positions of the ions are reversed. Is Ca3N2 ionic or covalent? Ionic bond: Calcium Nitride (Ca3N2).

Calcium nitride decomposes to form calcium hydroxide and release ammonia in the case of water. It is soluble in dilute acid and decomposes in anhydrous alcohol. It can also react with hydrogen to make calcium hydride and calcium amide.
Uses of Ca3N2 powder
Calcium nitride is a significant chemical reagent and has important uses in the chemical industry. So, what is calcium nitride used for? Because of their chemical inertness and ability to withstand high temperatures, interstitial nitrides are useful in several high-temperature applications, including their use as crucibles and high-temperature reaction vessels. Calcium nitride can be used to obtain reactive nitride ions. Besides, Calcium hydride can be produced by heating calcium nitride with hydrogen at temperatures above 350 °C.
Why can't Ca3N2 be written like N2Ca3? Now, why can't Ca3N2 ever be written like N2Ca3? The positive must be listed first, and then the negative. There are two rules to follow when writing formulas for ionic compounds. One has to do with charges and the other has to do with which atom to write first and which one to write second.