Chemistry

Avogadro's number is the number of "elementary entities" (usually atoms or molecules, ions, electrons, protons etc.) in one mole. Its value is 6.0221415 × 1023.

There are 6.0221415 × 1023 atoms per mole of atoms. This number is known as Avogadro's number.

Compare this to: There are 6 bottles in one six-pack, 12 eggs in one dozen, 12 dozen eggs in one gross (144) etc. They are just numbers.

Note: A mole is a useful quantity, because the mass of 1 mole of a substance will have the same 'grams' as the atomic mass. Example Helium with 2 protons and 2 neutrons, has atomic mass = 4. One mole of Helium atoms have a mass of 4 grams.

If you had a mole of sheets of paper stacked up, it would be 125 BILLION times taller than the distance between Earth and the moon! Now that's a big stack of paper! A mole of water molecules, on the other hand, is about is about 1/2 a fluid ounce of water!

The atoms in a water molecule (H2O) has an atomic mass of (1 + 1 + 16 = 18), so 1 mole of water is 18 grams. With the density of liquid water at nearly 1 gram/milliliter, this mole of water has a volume of 18 milliliter = 0.61 fluid ounce.

So for example, if you have 1 mole of atoms, you have 6.02 x 1023 atoms.

Or, if you have 2 moles of atoms, then you have 1.204 x 1024 atoms.

In other words, to convert from moles of atoms to number of atoms, multiply by 6.02 x 1023.

If instead you have 1.8 x 1023 atoms, then to find the number of moles, just divide:

1.8 x 1023 ÷ 6.02 x 1023 = 0.299 moles.

In other words, to convert from number of atoms to moles, divide by 6.02 x 1023.

Avogadro's number is 6.02*10^23.