molar mass of PF5 = 125.966 g/mol
125 g PF5 × (1 mol PF5/125.966 g PF5) = 0.992 mol PF5
0.992 mol PF5 × (6.022 × 10^23 molecules PF5);
= 5.97 × 10^23 molecules PF5
Since there 5 fluorine atoms per molecule of PF5,
(5.97.× 10^23 molecules PF5) × (5 atoms F/1 molecule PF5)
= 2.99 × 10^24 atoms F