You have to go from grams --> moles --> molecules. You can find the equation online.
First you have to find the molar mass of AlF3 which is 83.98 g/mol.
To convert it to moles you simply
450.0 grams × [tex]\frac{1 mol}{83.98 grams}[/tex] = 5.358 mol
To convert mol to molecules: (multiply by Avogadros # = 6.022*10^23)
5.358 mol × [tex]\frac{6.022*10^2^3}{1mol}[/tex] = [tex]3.23 *10^{24}[/tex]
