1. Determining Formulas The Criss-Cross Method
Examples
Na+1 + O-2 
Ca+2 + P-3 
C+4 + O-2 
Na2O
Ca3P2
C2O4  reduced to CO2

2. deduce a chemical formula.
Naming Compounds
Chemical Nomenclature--> system used to name chemical substances.
The Name of a compound indicates the composition of the substance.
From the name one can
deduce a chemical formula.

3. Naming Binary Compounds
The first element is named as usual but only a stem of the second is used followed by the suffix “ide”
For example: MgCl2 is Magnesium chloride
: Al2O3 is Aluminum Oxide
The Chlorine and Oxygen must change their suffix from “ine” and “ygen” to “ide” !

4. Naming Compounds Try these! NaCl Li3N MgI2 Sodium Chloride
Lithium Nitride
Magnesium Iodide

5. Stock System for Transitional Metals
A compound that contains a transitional metal must be named so that the oxidation # of the metal is identified.
A Roman numeral is placed after the metal. It represents the oxidation # of the metal.
Ex. FeCl3  Iron (III) Chloride
CuCl2  Copper (II) Chloride

6. Assigning Oxidation # Transitional Metals
The total charge on any compound or molecule
is always equal to zero.
To determine unknown oxidation #s, add up the oxidation #s of the Cation and Anion and set them equal to zero. (Create an algebra formula and solve for X.)
Example Cr2O3 total charge = 0
Cr = x , O = -2
Formula 2x + 3(-2)= 0  2x-6= 0 x= +3 Cr= +3

7. Naming Transitional Metal Compound
Name These,
FeCl2
CrO2
NiP
Iron(II) Chloride
Chromium(IV) Oxide
Nickel(III) Phosphide

8. Naming compounds that contain Poly-atomic ions
Identify the formula using Criss-Cross method.
Name the cation (metal) 1st . If a transitional metal determine the charge and assign the Roman numeral that is equivalent to the charge.
Name the poly-atomic ion using its normal name.
Ex. Calcium + Nitrate  Calcium Nitrate
Ca (NO3) -1  Ca(NO3)2

9. Naming compounds that contain Poly-atomic ions
Name These,
Ba3(PO4)2
CrSO4
W(OH)3
Barium Phosphate
Chromium(II) Sulfate
Tungsten(III) Hydroxide

10. Naming Molecules (the old system)
If two non-metals are bonded covalently, the name can be shown using prefixes.
The number of atoms for each element in a molecule is usually indicated by the prefix:
mono atom - hexa atoms
di atoms - hepta atoms
tri atoms - octa atoms
tetra atoms
penta atoms

11. Naming Molecules Examples: nitrogen dioxide is NO2
dinitrogen pentoxide is N2O5
phosphorus tribromide is PBr3
The prefix represents the subscript.
 If the subscript is one mono is not needed.

12. Use Old Naming system and Stock system
Binary Molecules
Name these :::
Use Old Naming system and Stock system
PCl3
PCl5
SO2
Phosphorus TriChloride
Phosphorus(III) Chloride
Phosphorus PentaChloride
Phosphorus(V) Chloride
Sulfur Dioxide
Sulfer (IV) Oxide