Avogadro's number (how we count atoms)

Atoms and molecules are really really small, so it would take a very very long time to count them.
How do we measure them then?
A man named Amedeo Avogadro proposed that the number of atoms in 12 g's of carbon can be equal to a constant(which is equal to 1 mol of carbon). 
What is a mol? No not a mole!

A mole(mol) is just a unit of measurement for atoms, molecules and formula units, like how a dozen is equal to twelve or how a millennium is 1000.
What is Avogadro's #? 

So how big is a mol? If we used real life a real life example, 1 mol of meters would cross the galaxy over 3000 times.                                                                 

Example of figuring out how many moles is in an element

A sample of  Hydrogen contains 2.2 times 10 to the power of 21 atoms. How many moles of carbon is this?

In order to figure out this problem, we use dimensional analysis. You want to figure how many moles there are and so to do this, you want to cancel out atoms, so you use Avogadro's number!

So you write 2.2 x 10^21 atoms times 6.02 x 10^23 moles/atoms. The atoms cancel each other out and you end up with 1.32 x 10 to the power of 45!