Warm Up: To be Turned inPredict the molecular shape for the

following compounds:

CCl4 CO2

Chemical Names and Formulas

Significance of Chemical FormulasSome compounds are better known

by their common namesProvides no information about the chemical

Ionic compounds- represents one formula unit—the simplest ratio of the compound’s cations and anions

EX: Al2(SO4)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 numbersBased on the movement of electrons

between atomsGroups 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 FormulasWrite the atoms side by side along

with their oxidation numbers, starting with the metal

Al3+O2-

Cross over the oxidation numbers by using the absolute value of each atom’s oxidation number as the subscript for the other ion.

Al23+O32−

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.

Al23+O32−

(2 × 3+ = 6+) (3 × 2- = 6-)Al2O3

Naming Ionic CompoundsTwo part name

Write the metal firstWrite the nonmetal second

Drop the original ending and replace with –ide

Ex: MgCl2 = magnesium chloride; KI= potassium iodide

Transition MetalsSome 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 metalEx: FeO = Iron(II) oxide; SnO2 = Tin(IV) oxide

Polyatomic ionsIons formed by more than one atomNaming system: write the metal followed

by the name of the polyatomic ion (except for NH4

+, which is always names first)Ex: NaNO3 = sodium nitrate

+1 -1 -2 -3

Ammonium NH4+ Acetate C2H3O2

- Carbonate CO32- Phosphate PO4

3-

Cyanide CN- Chromate CrO42-

Hydroxide OH- Dichromate Cr2O7

2-

Nitrate NO3- Sulfate SO4

2-

Nitrite NO2- Sulfite SO3

2-

Perchlorate ClO4-

Permanganate MnO4

-

Homework: Due 10/30/2012Write formulas for the compounds formed between the following atoms:

aluminum and bromine

sodium and oxygen

magnesium and iodine

Pb2+ and O2−

Sn2+ and I−

Fe3+ and S2−

Cu2+ and NO3−

NH4+ and SO4

2−