Here's how to calculate the number of atoms in 6PCl5:

1. Identify the elements and their subscripts:

* P (Phosphorus): 1 atom per molecule

* Cl (Chlorine): 5 atoms per molecule

2. Account for the coefficient:

* The coefficient "6" in front of the formula indicates that there are 6 molecules of PCl5.

3. Calculate the total number of each atom:

* Phosphorus: 6 molecules * 1 P atom/molecule = 6 P atoms

* Chlorine: 6 molecules * 5 Cl atoms/molecule = 30 Cl atoms

4. Calculate the total number of atoms:

* Total atoms: 6 P atoms + 30 Cl atoms = 36 atoms

Therefore, there are 36 atoms in 6PCl5.