1. Topic: Chemical Formulas

2. Subscripts in Chemical Formulas
numbers inside formulas
lowered below line of type
show # of atoms of each element
No subscript – understood to be 1 S8
8 is the subscript, so there are 8 Sulfur toms

3. Chemical Formulas H2O has: 2 hydrogens and 1 oxygen
NH3 has: 1 nitrogen and 3 hydrogens
CH4 has ?
CO2 has ?
AgNO3 has ?
1 carbon and 4 hydrogen
1 carbon and 2 oxygen
1 silver, 1 nitrogen, 3 oxygen

4. # atoms in formulas Subscript outside ( ) multiplied by
subscript inside ( ) = # of atoms
Al(NO3)3
Al =
N =
O =
Total = 1
1 x 3 = 3
3 x 3 = 9
13 atoms

5. Coefficients Numbers in front of formulas
Refers to everything following in formula
No coefficient? It’s understood to be 1
4CO2
4 is the coefficient

6. Coefficients 2H2O means 2(H2O) To count atoms -
multiply: coefficient x subscript
2 x 2 = 4 H’s
2 x 1 = 2 O’s

7. Chemical Formulas 3H2O has: 6 hydrogens and 3 oxygens
2NH3 has: 2 nitrogen and 6 hydrogens
4CH4 has ?
3CO2 has ?
2AgNO3 has ?
4 carbon and 16 hydrogen
3 carbon and 6 oxygen
2 Ag, 2 N, 6 O

8. HI
CH4

10. Lets Try one more
2Al(NO3)3

11. Hydrates
group of salts that have water molecules stuffed in their empty spaces
Ex: CuSO45H2O
 means “is associated with” or “included”
DOES NOT refer to multiplication
Not a true chemical bond:
structure is definite so
# empty spaces is definite &
# water molecules is definite

12. CuSO45H2O Count up the atoms! Cu x 1 S x 1 O x 4 H x 10 O x 5
total = 21 atoms

13. 5[CuSO45H2O] Count up the atoms! Coefficients x Subscripts Cu x 5
O x 20 (5x4)
H x 50 (5x5x2)
O X 25 (5x5)
total = 105 atoms
Coefficients x Subscripts