Here's how to determine the number of hydrogen atoms in 2NH3:

* NH3 (Ammonia): Each ammonia molecule (NH3) contains 3 hydrogen atoms.

* 2NH3: The coefficient "2" in front of NH3 means we have two ammonia molecules.

* Total Hydrogen Atoms: Therefore, 2NH3 has a total of 2 molecules * 3 hydrogen atoms/molecule = 6 hydrogen atoms.