# How do you find the number of molecules or ions of 4.5 mol BCl_3?

The number of MOLECULES of $B C {l}_{3}$ is $4.5$ $\times$ ${N}_{A}$, where ${N}_{A}$ is Avogadro's number.
In one mole of stuff (atoms, molecules, eggses), there are ${N}_{A}$ individual items of that stuff.
So, there are $4.5$ $\times$ ${N}_{A}$ $B C {l}_{3}$ molecules; i.e. $4.5$ $\times$ $6.022 \times {10}^{23}$ $\cong$ $27 \times {10}^{23}$ individual molecules of $B C {l}_{3}$. How many actual ATOMS in this molar quantity of BCl_3??