There are 8.61 × 10²⁰ atoms in 0.290 g P₂O₅.
Step 1. Convert grams of P₂O₅ to moles of P₂O₅.
[tex]\text{Moles of P}_{2}\text{O}_{5} = \text{0.290 g } \text{P}_{2}\text{O}_{5} \times \frac{\text{1 mol }\text{P}_{2}\text{O}_{5}}{\text{141.94 g }\text{P}_{2}\text{O}_{5}} = \text{0.002 043 mol } \text{P}_{2}\text{O}_{5} \\[/tex]
Step 2. Convert moles of P₂O₅ to molecules of P₂O₅.
[tex]\text{Molecules of } \text{P}_{2}\text{O}_{5} = \text{0.002 043 mol } \text{P}_{2}\text{O}_{5} \times \frac{6.022 \times 10^{23}\text{ molecules }\text{P}_{2}\text{O}_{5}}{\text{1 mol } \text{P}_{2}\text{O}_{5}}\\[/tex]
[tex]= 1.23 \times10^{21}\text{ molecules } \text{P}_{2}\text{O}_{5}\\[/tex]
Step 3. Convert molecules of P₂O₅ to atoms.
There are seven atoms in 1 mol P₂O₅.
∴ [tex]\text{Total atoms} = 1.23\times 10^{21 }\text{ molecules }\text{P}_{2}\text{O}_{5} \times\frac{\text{7 atoms}}{\text{1 molecule }\text{P}_{2}\text{O}_{5}} = 8.61 \times 10^{21}\text{ atoms}\\[/tex]
