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

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.

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” !

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

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

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

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

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+2 + (NO3) -1  Ca(NO3)2

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

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 - 1 atom - hexa - 6 atoms di - 2 atoms - hepta - 7 atoms tri - 3 atoms - octa - 8 atoms tetra - 4 atoms penta - 5 atoms

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.

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