Here's how to figure out the number of atoms in a molecule of trinitrotoluene (TNT):

1. The Chemical Formula:

The chemical formula for TNT is C₇H₅N₃O₆.

2. Counting the Atoms:

* Carbon (C): 7 atoms

* Hydrogen (H): 5 atoms

* Nitrogen (N): 3 atoms

* Oxygen (O): 6 atoms

3. Total Atoms:

7 + 5 + 3 + 6 = 21 atoms

Therefore, there are 21 atoms in one molecule of trinitrotoluene (TNT).