The atomic mass of ammonia (NH3) can be calculated by adding the atomic masses of its constituent atoms: nitrogen (N) and hydrogen (H).

- Nitrogen (N): The atomic mass of nitrogen is approximately 14.007 atomic mass units (amu).

- Hydrogen (H): The atomic mass of hydrogen is approximately 1.008 amu.

Since there is one nitrogen atom and three hydrogen atoms in an ammonia molecule, we can calculate the atomic mass of ammonia as follows:

Atomic mass of ammonia = (1 × atomic mass of N) + (3 × atomic mass of H)

Atomic mass of ammonia = (1 × 14.007 amu) + (3 × 1.008 amu)

Atomic mass of ammonia ≈ 14.007 amu + 3.024 amu

Atomic mass of ammonia ≈ 17.031 amu

Therefore, the atomic mass of ammonia is approximately 17.031 atomic mass units.