1. Compounds

2. Compound:
a substance made up of atoms of different elements joined together (involves a chemical change)

3. Example: *There is no atom of water.
*Two atoms of hydrogen join with one atom of oxygen. (chemical bond)
*The smallest unit of water is called a molecule.

4. the arrangement of symbols and numbers that describe a compound
Chemical Formula:
the arrangement of symbols and numbers that describe a compound

5. Example: H2O H = Hydrogen How many atoms of hydrogen?

6. O = Oxygen
If there is no number behind the element symbol, there is just one atom of that element.
Therefore, there is only 1 atom of oxygen in H20.

7. NaCl 2 How many elements? Sodium, chlorine Name of elements
Atoms of each element
Na = 1
Cl = 1
Total # of atoms 2
Name of compound
Table Salt

8. Your Turn

9. Other Chemical Formulas

10. nitrogen dioxide
one atom of nitrogen
two atoms of oxygen
NO2

11. aluminum oxide
two atoms of aluminum
three atoms of oxygen
Al2O3

12. acetylene
two atoms of carbon
two atoms of hydrogen
C2H2

13. Na2CO3 sodium carbonate two atoms of sodium one atom of carbon
three atoms of oxygen
Na2CO3

14. C6H12O6 glucose six atoms of carbon twelve atoms of hydrogen
six atoms of oxygen
C6H12O6

15. ammonia
one atom of nitrogen
three atoms of hydrogen
NH3

16. benzene
six atoms of carbon
six atoms of hydrogen
C6H6

17. Recipes for Compound Molecules

18. Write the following as a formula:
# 1. hydrogen peroxide
two atoms of hydrogen, two atoms of oxygen
H2O2

19. Here are some formulas. You write out the recipe.

20. # 1. aluminum phosphate AlPO4 one atom of aluminum
one atom of phosphorus
four atoms of oxygen

21. Do you know how to read formulas
Do you know how to read formulas? Read through the following formulas for molecules of different compounds. Then tell how many different elements and atoms are in each molecule.

22. # 4. Fe2O3
# of elements 2 5
# of atoms
common name
rust

23. Click for Video Clip on Compounds