A 1.00 carat pure diamond has a mass of 0.2 grams. How many carbon atoms are there within this diamond?
In this example you have 0.2 grams of carbon atoms. The first step is to find out how many moles this is.
The molar mass of carbon is 12.01 g/mol, you have 0.2 gram so:
The number of atoms can be calculated using Avogadro's constant that says that 1 mole of any element contains