1. COUNT ATOM How to count atoms

2. 2H 2 O COEFFICIENT SUBSCRIPT

3. 2H 2 O 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

4. 2H 2 O 2MOLECULES!!!!

5. 2H 2 O 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.

6. How many hydrogen atoms are present? 4 How many oxygen atoms are present? 2

7. 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

8. Let’s try an example: 4CaCO 3

10. 1. Write down symbols 4CaCO 3 Ca C O

11. Write down the coefficient next to each symbol 4CaCO 3 Ca C O 444444

12. Multiply by the subscript 4CaCO 3 Ca C O 444444 XXXXXX 113113

13. Multiply… 4CaCO 3 Ca C O 444444 XXXXXX 113113 ====== 4 12

14. Add totals together to get the total amount of atoms 4CaCO 3 Ca C O 444444 XXXXXX 113113 ====== 4 12 20 atoms

15. 3CO 2

17. 2C 6 H 12 O 6 GLUCOSE

18. 2C 6 H 12 O 6

19. 6K 2 SO 4

21. CaMg(CO 3 ) 2

23. 3Pb(NO 3 ) 2