What is the chemical formula for ammonia?

Ammonia is a compound consisting of nitrogen and hydrogen, with the chemical formula representing one nitrogen atom bonded to three hydrogen atoms. This is distinctly reflected in the formula NH3, where the "N" stands for nitrogen and the three "H" symbols indicate the three hydrogen atoms that are covalently bonded to the nitrogen atom.

In the context of the other options, NH4 represents ammonium, which is a positively charged ion (cation) derived from ammonia but has a different structure. NH2 describes the amide functional group, which does not encompass the full tetrahedral geometry or the characteristic properties of ammonia. N2H6, on the other hand, suggests a molecular structure containing two nitrogen atoms and six hydrogen atoms, which is not representative of ammonia but rather a different compound called hydrazine.

Thus, the formula NH3 correctly identifies ammonia and reflects its molecular composition accurately.