How many grams of fluorine are contained in 8 molecules of boron trifluoride?

Each molecule of boron trifluoride (BF3) contains 3 fluorine atoms. Hence, 8 molecules BF3 would contain 24 fluorine atoms. Calculate the number of moles of fluorine,

(24 fluorine atoms) x (1 mole / 6.022 x10^23 atoms) = 3.985 x10^-23 moles fluorine

Multiply this number of moles by the molar mass of fluorine which is equal to 19 g/mol. The answer would be 4.78x10^-22 grams.