1. COMPOUNDS

2. Compounds Pure substances that are made of more than one element are called compounds (molecules) Compounds are two or more elements chemically combined.

3. Examples of compounds SALT: NaCl SUGAR:C 12 H 22 O 11 WATER: H 2 O

4. BREAKING DOWN COMPOUNDS Heat can break down compounds. Electric energy can break down compounds that cannot be separated using heat

5. Molecules Compounds are made of molecules Molecules are two or more atoms chemically combined Molecules are the smallest particle of a compound that has all the properties of that compound

6. Two Ways Molecules Form 1.Ionic Bonding - Bonded by electric charge. 2.Covalent - Share outermost electrons.

7. Chemical Formulas Chemical formulas are combinations of chemical symbols Short way to represent chemical substances Most chemical formulas represent compounds

8. Examples of Chemical Formulas Ammonia: NH 3 1 atom of nitrogen, 3 atoms of hydrogen Silver nitrate: AgNO 3 1 silver, 1 nitrogen, 3 oxygen Carbon dioxide: CO 2 1 carbon, 2 oxygen

9. Molecules of elements Sometimes elements are found in nature as molecules –Hydrogen = H 2 –Oxygen = O 2 –Nitrogen = N 2 –Chlorine = Cl 2 HH Drawing chemical equations Hydrogen oxygen CC NN Nitrogen

10. Subscripts The small numbers you place to the right of the symbol. Must be placed lower –EX: C 2 H 4 O 2 –Subscripts apply to what they follow Gives the number of atoms of the element in the compound. –2 carbon, 4 hydrogen, 2 oxygen If there is only 1 atom, the subscript is not written. –Example: NaHCO 3

11. Coefficients Number placed in front of a molecule or compound. Applies to the entire compound. Coefficients and Subscripts multiply.

12. Practice counting atoms List the elements in each of the following compounds. Calculate how many atoms of each element are present. 1.NaHCO 3 4. C 6 H 12 O 6 2.Mg(OH) 3 5. 2H 2 O 3.3H 3 PO 4 6. MgO

13. Answers to Counting Atoms 1.NaHCO 3 1 sodium, 1 hydrogen, 1 carbon, 3 oxygen 2. Mg(OH) 3 1 magnesium, 3 oxygen, 3 hydrogen 3. 3H 3 PO 4 9 hydrogen, 12 oxygen 3 phosphorous 4.C 6 H 12 O 6 6 carbon, 12 hydrogen 6 oxygen 5. 2H 2 O 4 hydrogen, 2 oxygen 6. MgO 1 magnesium, 1 oxygen

14. Chemical Equations Used to describe a chemical process or reaction Charcoal burning is a chemical reaction –1 Carbon atom plus 1 oxygen atom produces carbon dioxide molecules OR - C + O 2 CO 2

15. oo Look at Chemical Formulas -C + O 2 CO 2 -This says that 1 carbon atom and an oxygen molecule create carbon dioxide -The arrow means produces - C oo C

16. Another Chemical Equation H 2 + O 2 H 2 OH 2 + O 2 H 2 O 1 hydrogen molecule combines with 1 oxygen molecule to produce water.1 hydrogen molecule combines with 1 oxygen molecule to produce water. Problem with the equation—what is it?Problem with the equation—what is it? Numbers do not balance on each sideNumbers do not balance on each side –Look at the oxygen atom

17. Correcting the water equation H 2 + O 2 H 2 O There are 2 hydrogen atoms on each side so that is correct There are 2 oxygen atoms on the left side, but only one on the right side. You need to balance both sides 2H 2 + O 2 2H 2 O Now there are even number of atoms on each side (4 hydrogen, 2 oxygen)

18. Lets try another one P 4 + O 2 P 2 O 3 How many phosphorous atoms on each side? –4 on the left, 2 on the right How many oxygen atoms on each side? –2 on the left, 3 on the right What can we do to balance it? P 4 + 3O 2 3P 2 O 3

19. Let’s practice again N 2 + H 2 NH 3 How many nitrogen and hydrogen atoms on each side? –Left: 2 nitrogen and 2 hydrogen –Right: 1 nitrogen and 3 hydrogen How can we balance it? N 2 + 3H 2 2NH 3

20. another—you WILL understand this AlBr3 + K KBr + Al What elements are involved? –Aluminum, bromine and potassium How many atoms of each element are on each side of the equation –Left side: 1 aluminum, 3 bromine, 1 potassium –Right side: 1 potassium, 1 bromine and 1 aluminum

21. So the answer to the question What is the balanced equation –AlBr 3 + 3K 3KBr + Al How many atoms of each element are there now on each side –Left side: 1 aluminum, 3 bromine, 3 potassium –Right side: 3 potassium, 3 bromine and 1 aluminum

22. Now for a harder one LiNO 3 + CaBr 2 Ca(NO 3 ) 2 + LiBr What atoms are involved? –Lithium, nitrogen, oxygen, calcium, bromine How many atoms on each side? –Left: 1 Li, 3 O, 1 Ca, 3 Br –Right: 1Ca, 2 N, 6 O, 1 Li, 1 Br

23. What is the balanced equation 2LiNO 3 + CaBr 2 Ca(NO 3 ) 2 + 2LiBr How many atoms are there now? 2 Li, 2 N, 6 O, 1 Ca, 2 Br on each side.

24. Coefficient Those numbers we added to the front of the formula is called the coefficient. This is how you balance an equation.

25. THE END