Question: determine how many atoms of each element are present?
Answer: To calculate the number of atoms in a sample, you need to find how many moles of the element the sample contains. A mole is a unit chemists use. It's equal to Avogadro's number (6.02 X 1023) of atoms. By definition, the weight of one mole of an element (its molar mass) is equal to its atomic weight in grams.