To find how many atoms are in the compound, we first have to find how many moles there are. The numbers in the subscript tell you how many moles of each element are present in the compound. Therefore, to find the number of total moles, we can add up each of the numbers in the subscript:
Cu₂Mg₁H₁O₁ *when there is no number under an element, it is implied that there is 1 mole of the element
2+1+1+1=5 moles
We can then use Avogadro's number and dimensional analysis to find how many atoms are in the compound (Avogadro's number is 6.02x10^23):
5 moles (6.02x10^23/1 mole)= 3.01x10^24 atoms
