Warm Up: To be Turned in Predict the molecular shape for the following compounds : CCl 4 CO 2

Chemical Names and Formulas

Significance of Chemical Formulas Some compounds are better known by their common names Provides no information about the chemical Ionic compounds- represents one formula unit—the simplest ratio of the compound’s cations and anions EX: Al 2 (SO 4 ) 3 Subscript 3 refers to everything inside parentheses giving 3 sulfate ions, with a total of 3 sulfur atoms and 12 oxygen atoms. Subscript refers to 2 aluminum atoms. Subscript refers to 4 oxygen atoms.

Assigning Oxidation numbers Based on the movement of electrons between atoms Groups 1, 2, and 13 have oxidation numbers of +1, +2, +3, respectively Groups 15,16,17 have oxidation numbers of -3, -2, -1, respectively

Writing Ionic Chemical Formulas Write the atoms side by side along with their oxidation numbers, starting with the metal Al 3+ O 2- Cross over the oxidation numbers by using the absolute value of each atom’s oxidation number as the subscript for the other ion. Al 2 3+ O 3 2−

Writing Ionic Chemical Formulas, Cont. Multiply the oxidation number by the number of atoms for each part of the formula. The two number should be equal but opposite in value. Al 2 3+ O 3 2− (2 × 3+ = 6+) (3 × 2- = 6-) Al 2 O 3

Naming Ionic Compounds Two part name Write the metal first Write the nonmetal second Drop the original ending and replace with –ide Ex: MgCl 2 = magnesium chloride; KI= potassium iodide

Transition Metals Some transition metals (Fe, Cu, Pb, Sn, Cr, etc.) can form ions with more than one possible charge We identify the various compounds using the Stock System. Write a Roman Numeral immediately after the metal Ex: FeO = Iron(II) oxide; SnO 2 = Tin(IV) oxide

Polyatomic ions Ions formed by more than one atom Naming system: write the metal followed by the name of the polyatomic ion (except for NH 4 +, which is always names first) Ex: NaNO 3 = sodium nitrate Ammonium NH 4 + Acetate C 2 H 3 O 2 - Carbonate CO 3 2- Phosphate PO 4 3- Cyanide CN - Chromate CrO 4 2- Hydroxide OH - Dichromate Cr 2 O 7 2- Nitrate NO 3 - Sulfate SO 4 2- Nitrite NO 2 - Sulfite SO 3 2- Perchlorate ClO 4 - Permanganate MnO 4 -

Homework: Due 10/30/2012 Write formulas for the compounds formed between the following atoms: aluminum and bromine sodium and oxygen magnesium and iodine Pb 2+ and O 2− Sn 2+ and I − Fe 3+ and S 2− Cu 2+ and NO 3 − NH 4 + and SO 4 2−