How many atoms of fluorine are in a sample of 19 grams?

First, you must find the number of moles of copper that your sample has. This is calculated by #of moles = your sample mass (in grams) / atomic mass (in grams)

#of moles=19g/18.998g

#of moles = 1.0 moles present

Then to find the number of atoms present, we must multiply the number of moles present in the sample with Avogadro's number, which is 6.022x10^23 (this number is the number of atoms present in each mole)

# of atoms present in copper sample=1.0 (6.022x10^23)

#of atoms present in copper sample = 6.022x10^23