©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

H O2

Atomic Symbols

Water

©Dr. Mitchel Goodkin, 2007

H O2

Hydrogen Oxygen

©Dr. Mitchel Goodkin, 2007

H O2

Subscript

©Dr. Mitchel Goodkin, 2007

H O2

The Subscript only applies tothe symbol in front of it.

…so in this case, it means we have 2 Hydrogens

©Dr. Mitchel Goodkin, 2007

H O2

Even though there is nosubscript next to Oxygen,

it is implied that there is a 1,there’s no need to write it in.

1

©Dr. Mitchel Goodkin, 2007

Ammonia

Now look at these common molecules…

NH3

How many of each atom do you see?

N= H=31©Dr. Mitchel Goodkin, 2007

Methane

Now look at these common molecules…

CH4

How many of each atom do you see?

C= H=41©Dr. Mitchel Goodkin, 2007

Hydrogen Peroxide

Now look at these common molecules…

H O2

How many of each atom do you see?

2

H= O=22©Dr. Mitchel Goodkin, 2007

Rubbing Alcohol

Now look at these common molecules…

C H OH73

How many of each atom do you see?

C= H= O=3 8 1©Dr. Mitchel Goodkin, 2007

Caffeine

Now look at these common molecules…

C H N O2

How many of each atom do you see?

48 10

C= H= N= O=8 10 4 2

©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

A coefficient means that you havemore than one of that particularmolecule. You can ONLY put a

coefficient in the front of a molecule.Never place one in the middle.

3H O2

©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

3H O2

Is the same as….

H O2 H O2 H O2+ +©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

3H O2

Which means we have….

H O

H O2 H O2 H O2+ +

36©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

3H O2OR…we can use the

Distributive Property of math !!

©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

3H O2Is the same as….

3(H O)2©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

3(H O)2

3 x 2 = 6 H’s©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

3(H O)2

3 x 1 = 3 O’s©Dr. Mitchel Goodkin, 2007

Look at this sample molecule.

3(H O)2

H= 6 O=3©Dr. Mitchel Goodkin, 2007

Rubbing Alcohol

What if we had more than one Alcohol molecule ?

4C H OH73

How many of each atom do you see?

C= H= O=©Dr. Mitchel Goodkin, 2007

What if we had more than one Alcohol molecule ?

4C H OH73Is the same as….

C H OH73 C H OH73+ +

C H OH73 C H OH73+©Dr. Mitchel Goodkin, 2007

Rubbing Alcohol

Let’s look at that same molecule another way…

4C H OH73

How many of each atom do you see?

C= H= O=12 32 4

©Dr. Mitchel Goodkin, 2007

Remember, this is the same as…

4(C H OH)73

4 x 3 = 12 C’s©Dr. Mitchel Goodkin, 2007

Remember, this is the same as…

4(C H OH)73

4 x 7 = 28 H’s©Dr. Mitchel Goodkin, 2007

Remember, this is the same as…

4(C H OH)73

4 x 1 = 4 O’s©Dr. Mitchel Goodkin, 2007

Remember, this is the same as…

4(C H OH)73

4 x 1 = 4 H’s©Dr. Mitchel Goodkin, 2007

4(C H OH)73

But wait ! Hydrogen appears twice !!!

No problem…after you’re done,just add all the Hydrogens together !

4 x 1 = 4 H’s4 x 7 = 28 H’s 28 H’s

+ 4 H’s

32 H’s