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How to Find Out How Many Atoms Are in an Element Based on Grams

Atoms are so tiny that even a small object like a pencil eraser contains a enormous number of them. Consequently, chemists usually denote the number of atoms or molecules present in terms of moles, where one mole is about 6.02214 x 10^23 atoms, molecules, particles, etc. The concept of the mole and the periodic table make it really simple to figure out how many atoms are present in a pure sample of an element. All you need is the weight in grams.

Things You'll Need

Periodic table

Instructions

- 1
  Find your element on the periodic table. Gold, for example, is in column 11, period 6. Look at the box containing your element. You'll notice there are several numbers surrounding the symbol for the element. The number directly below the name is the atomic mass in grams per mole. Gold's atomic mass, for example, is 196.97 grams per mole.
- 2
  Divide the weight of your sample in grams by the atomic weight in grams per mole. If you have a 196.97 gram sample of gold, for example, you have one mole of gold.
- 3
  Multiply the number of moles by 6.02214 x 10^23 atoms per mole if you need the actual number of atoms. In the case of gold, for example, one mole would be equal to 6.02214 x 10^23 atoms of gold.

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