Name: _______________________
Notes – Counting Atoms
Date: __________ /HW#: ____
Mr. Jensen/Period: _____
COUNT ATOM
(How to Count Atoms!)
2H2O
The coefficient gets applied to the ____________________ formula
-this means there are 2 molecules of water present!
-you ___________________ this number by every subscript in the formula
The subscript only gets applied to the ___________________________
-If there is no subscript present, it is assumed that there is only _____ atom of that element in the
molecule
How many hydrogen atoms are present?
How many oxygen atoms are present?
The easiest way to count atoms:
1. Write down all the symbols for all of the elements present in the formula
2. If there is a coefficient, write this number next to each of the symbols
3. Multiply the coefficient by the subscripts’ of each of the elements present in the formula
4. If there is parentheses than you need to multiply all atoms that are inside the parentheses by
the subscript
Let’s try some examples!