1. Balance some Equations:
Al + O Al2O3
Mg + P Mg3P2
CaCl2 + AgNO AgCl + Ca(NO3)2

2. There are 4 types of chemical reactions:
…Now that we know substances can react and change form, we need to know what they change into
There are 4 types of chemical reactions:
Synthesis
Decomposition
Single displacement (single replacement)
Double displacement (double replacement)

3. Two or more substances combine to form another substance
Synthesis Reaction
Two or more substances combine to form another substance

4. Decomposition Reaction
One substance breaks down into two or more substances ( reverse of synthesis)

5. One element replaces another element in a compound
Single Displacement
One element replaces another element in a compound

6. Double Displacement
The positive ion of one compound replaces the positive ion of another to form two new compounds

7. What type of reaction is each of the following:
2Fe + O FeO
Mg + 2HCl H2 + MgCl2
H2CO CO2 + H2O
2Al + 3Pb(NO3) Pb + 2Al(NO3)3
2KI + Pb(NO3) PbI2 + 2KNO3
synthesis
Single replacement
decomposition
Single
replacement
Double
replacement

8. And Balance some Equations!!!

9. I remember that from Physical Science in high school!!
Have you ever wondered why Calcium and Nitrogen always combine to give you Ca3N2?
Not for sure, but I know it has something to do with Oxidation #’s!
I remember that from Physical Science in high school!!

10. The Oxidation number is the “charge” of an atom once it has gained or lost electrons to become stable!

11. Oxidation #

12. Forming Simple Binary Compounds using Oxidation #’s
Remember:
Metals lose electrons
Form + ions
Nonmetals gain electrons
Form – ions
“We want to combine a metal with a nonmetal to form a binary compound!!!”

13. Steps in writing chemical formulas:
Write down the symbol for the element with the oxidation # written as a superscript.
If the oxidation #’s are the same(don’t worry about + or -), then do nothing. Just write down the symbols.
Ex. Write the chemical formula for the compound formed from the joining of Magnesium and Sulfur.
Mg2+S-2
MgS

14. Writing Chemical Formulas with same Oxidation #’s:
Combine Sodium and Chlorine
Na+1Cl-1
NaCl
Combine Calcium and Oxygen
Ca+2O-2
CaO
Combine Potassium and Fluorine
K+1F-1 KF

15. Steps in writing chemical formulas(cont):
If the oxidation #’s are not the same, cross the oxidation #’s and place as subscripts(Do not write the + or –).
One’s are understood and should not be written!!
Ex. Write the chemical formula for the compound formed from the joining of Magnesium and Chlorine.
Mg+2Cl-1
MgCl2

16. Writing Chemical Formulas with different Oxidation #’s:
Combine Sodium and Sulfur
Na+1S-2
Na2S
Combine Calcium and Iodine
Ca+2I-1
CaI2
Combine Aluminum and Fluorine
Al+3F-1
AlF3

17. I am sure at this point, some of you are wondering why we have to “cross” the oxidation #’s. What’s the point?
Well, I will tell you!!

18. The Sum of the Oxidation #’s of any neutral compound must be ZERO!!!
Have your teacher verify it for you!!!

19. What is a Polyatomic Ion?
Polyatomic ions are electrically charged collections of two or more atoms.
“Polyatomic ions usually have a charge because the collection of atoms has either gained an extra electron or else it has lost an electron.”
“Look on your Formula sheet for a list of common Polyatomic Ions!”

20. Polyatomic Ion Chart on Formula Sheet

21. Writing formulas for compounds using polyatomic ions:
Same rules apply!!
Oxidation #’s same, do nothing!
Ex. Combine Magnesium and Carbonate
Mg+2CO3-2
MgCO3

22. Writing formulas with Polyatomic ions(same Oxidation #)
Combine Sodium and Acetate
Na+1C2H3O2-1
NaC2H3O2
Combine Calcium and Sulfate
Ca+2SO4 -2
CaSO4
Combine Potassium and Nitrate
K+1NO3-1
KNO3

23. Polyatomic Ions with different Oxidation #’s:
Same rules apply.
If #’s are different, then cross #’s and place as subscripts (Do not write + or -).
If you write a subscript outside of a polyatomic ion, then you must put a parentheses around the entire polyatomic ion.
You cannot change the structure of the polyatomic ion.

24. Writing Chemical Formulas of with different Oxidation #’s:
Combine Sodium and Chromate
Na+1CrO4-2
Na2CrO4
Combine Calcium and Chlorate
Ca+2ClO3-1
Ca(ClO3)2
Combine Aluminum and Carbonate
Al+3CO3-2
Al2(CO3)3

25. Potassium and Permanganate
Barium and Sulfur
Ba+2S-2
BaS
Boron and Sulfur
B+3S-2
B2S3
Ammonium and Oxygen
NH4+1O-2
(NH4)2O
Potassium and Permanganate
K+1MnO4-1
KMnO4
Lithium and Selenium Li+1Se-2 Li2Se Calcium and Chlorate Ca+2ClO3-1 Ca(ClO3)2 Beryllium and Phosphorus Be+2P-3 Be3P2 Gallium and Carbonate Ga+3CO3-2 Ga2(CO3)3