Balance some Equations: Al + O2 Al2O3 Mg + P4 Mg3P2 CaCl2 + AgNO3 AgCl + Ca(NO3)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)

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

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

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

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

What type of reaction is each of the following: 2Fe + O2 2FeO Mg + 2HCl H2 + MgCl2 H2CO3 CO2 + H2O 2Al + 3Pb(NO3)2 3Pb + 2Al(NO3)3 2KI + Pb(NO3)2 PbI2 + 2KNO3 synthesis Single replacement decomposition Single replacement Double replacement

And Balance some Equations!!!

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!!

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

Oxidation #

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!!!”

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

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

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

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

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!!

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

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!”

Polyatomic Ion Chart on Formula Sheet

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

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

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.

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

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