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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
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Warm Up: To be Turned in Predict the molecular shape for the following compounds: CCl4CO2
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: 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 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 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 Compounds • Two part name • Write the metal first • Write the nonmetal second • Drop the original ending and replace with –ide • Ex: MgCl2 = 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; SnO2 = 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 NH4+, which is always names first) • Ex: NaNO3 = sodium nitrate
Homework: Due 10/30/2012 Write 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 SO42−