__COUNTING ATOMS__

When we want to know how
many atoms of a substance are in a sample of the substance that we can see,
counting the atoms individually is not practical. First of all, atoms are
so small that we cannot see them individually with our eyes. Second, we
would be counting for a very, very, very long time. Here is an example
for you to think about. The "lead" of a pencil is made of pure
carbon (graphite). Think about the size of the dot on a
"i" that you would write on your paper with
a pencil. Not very big. The number of
atoms of carbon in that dot is roughly equal to the population of the world -
about 6 billion! It would take a very long time to count that high.
And that is just for the number of atoms in the dot on an "i" on your paper!

So, you can see that we
have a problem if we try to count atoms individually. Instead, chemists
have come up with a system that is much easier for us to use. They (and
we) use a unit for counting the number of atoms in a sample of matter.
This unit is called the __MOLE__. One mole is equal to 6.022 x 10^{23}
atoms of any element. Using the term "mole" is similar to using
the word "dozen". We all know that a dozen means 12.
Well, a mole means 6.022 x 10^{23}.

Now, that is all well and
good. But we, as humans, still cannot see individual atoms. How can
we count them? The chemists came up with a way that we could measure moles.
Chemists decided that one mole of any element was equal to the average atomic
mass of that element in grams. They call it the "molar mass" of
the element. For example, the average atomic mass of carbon on the
Periodic Table is 12.011. Therefore, 12.011 grams of carbon is equal to
one mole of carbon. And, one mole of carbon is equal to 6.022 x 10^{23}
atoms of carbon. So, 6.022 x 10^{23} atoms of carbon have a mass
of 12.011 grams.

**1 mole = 6.022 x 10 ^{23} atoms or molecules = molar
mass of element or compound**

DIVIDE BY MOLAR MASS
(MM) DIVIDE
BY 6.022 X 10^{23}

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GRAMS
MOLES ATOMS OR

<------------------------------------
------------------------------------> MOLLECULES

MULTIPLY BY MOLAR MASS
(MM)
MULTIPLY BY 6.022 X 10^{23}