Dinitrogen tetrachloride.
The chemical name for N2Cl4 is dinitrogen tetrachloride.
N2Cl4 is the chemical formula for that compound; its name is dinitrogen tetrachloride.
Yes, N2Cl4 (tetra chlorodiazene) is a covalent compound. It is composed of nonmetal atoms (nitrogen and chlorine) which typically form covalent bonds by sharing electrons.
The formula is N2H4. You can easily figure this out on your own by recognizing what the prefixes on each element mean. For example, "di" means two and "tetra" means four. Then you just write the element's symbol (which is N for nitrogen and H for hydrogen) with the number that the prefix represents as a subscript.