# Count Atom COUNT ATOM How to count atoms 2H2O COEFFICIENT SUBSCRIPT

2H2O The coefficient gets applied to the ENTIRE formula -this means that there are 2 molecules of water present! -you MULTIPLY this number by every subscript in the formula

2H2O 2MOLECULES!!!! 2H2O The subscript only gets applied to the element it follows -If there is no subscript present, it is

assumed that there is only 1 atom of that element in the molecule. 2H2O How many hydrogen atoms are present? 4 How many oxygen atoms are present?

2 The easiest way to count atoms: 1. Write down all of 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 Lets try an example: 4CaCO3

4CaCO3 1. Write down symbols 4CaCO3 Ca C O

Write down the coefficient next to each symbol 4CaCO3 Ca 4

C 4 O 4

Multiply by the subscript 4CaCO3 Ca 4

X 1 C 4

X 1 O 4

X 3 Multiply 4CaCO3 Ca

4 X 1 = 4 C

4 X 1 = 4 O

4 X 3 = 12 Add totals together to get the

total amount of atoms 4CaCO3 Ca 4 X

1 = 4 C 4 X

1 = 4 O 4 X

3 = 12 3CO2 3CO2 2C6H12O6

GLUCOSE 2C6H12O6 6K2SO4 6K2SO4

CaMg(CO3)2 CaMg(CO3)2 3Pb(NO3)2 3Pb(NO3)2