Chemical Formulas and Compounds Oxidation Numbers

Monday, November 26 Take out a sheet of paper, title “Oxidation Numbers” Take out your Naming Compounds sheet that you received before Thanksgiving holiday. Hall Pass Policy: 2 per NINE WEEKS Document on Clipboard!

Tuesday, November 27 1-15 Compound Naming Problems: Any Questions? 16-30 = Homework Tonight Must complete entire sheet to retake Quiz 1 &2 Take out OXIDATION NUMBER notes from yesterday Hall Pass Policy: 2 per NINE WEEKS Document on Clipboard!

Nomenclature QUIZ 1 Ammonium Sulfate Sulfite Arsenate Phosphate Write the compound name: CaBr2 CoF3 SnI4 FeS Ca(OH)2 Write the formula: Sodium Iodide Calcium Chloride Potassium Sulfide Sodium Carbonate Calcium Nitrite Write the nomenclature: Ammonium Sulfate Sulfite Arsenate Phosphate Chlorate Chlorite Hydroxide Tetra- Penta-

Nomenclature QUIZ 2 NaI Carbonate CaO Sulfate K2O NO2 ˉ Ca(OH)2 Write the compound name: NaI CaO K2O Ca(OH)2 SO3 Write the formula: Sodium Hydroxide Lead (II) Nitrate Nitric Acid Barium Dioxide Tricalcium Dinitride Write the nomenclature: Carbonate Sulfate NO2 ˉ Nitrate Phosphate Hexa- Nona- H2SO4 Hydrochloric acid Nitric Acid

Nomenclature QUIZ 3 HNO2 Carbonate HClO3 Ammonium H2SO4 Hydroxide HCl Write the acid name: HNO2 HClO3 H2SO4 HCl H2CO3 Write the formula: Iron (II) Nitrate Sodium Fluoride Carbon Monoxide Potassium Sulfide Iron (III) Oxide Write the nomenclature: Carbonate Ammonium Hydroxide NO3 ˉ Perchlorate Sulfate Tri- Octa- Chlorite PO4 ³ˉ

Oxidation Numbers Oxidation Numbers the charge that it would have if all the bonds were removed along with the electron pairs that were shared with the central atom. Use to “keep track” of electrons In general when assigning oxidation numbers, shared electrons are assumed to “belong” to the more electronegative atom in each bond Oxidation numbers of carbon and hydrogen in ethane (number does not refer to valance electrons)

Oxidation Numbers Assigning Oxidation Numbers The atoms in a pure element have an oxidation number of zero Monatomic ions have an oxidation number equal to the charge of the ion The more-electronegative element in a binary compound is assigned a negative number equal to the charge it would have as an anion. Likewise for the less-electronegative element. Fluorine has an oxidation number of –1 in all of its compounds because it is the most electronegative element Oxygen usually has an oxidation number of –2 In peroxides, such as H2O2, oxygen’s oxidation number is –1 In compounds with fluorine, such as OF2, oxygen’s oxidation number is +2

Oxidation Numbers Assigning Oxidation Numbers Hydrogen has an oxidation number of +1 in all compounds containing elements that are more electronegative than it; it has an oxidation number of –1 with metals The algebraic sum of the oxidation numbers of all atoms in an neutral compound is equal to zero The algebraic sum of the oxidation numbers of all atoms in a polyatomic ion is equal to the charge of the ion Although rules 1 through 7 apply to covalently bonded atoms, oxidation numbers can also be applied to atoms in ionic compounds similarly

Oxidation Numbers Oxidation Numbers Sample Problem Assign oxidation numbers to each atom in the following compounds or ions: UF6 H2SO4

Oxidation Numbers Oxidation Numbers Sample Problem Solution Place known oxidation numbers above the appropriate elements Multiply known oxidation numbers by the appropriate number of atoms and place the totals underneath the corresponding elements The sum of the oxidation numbers must equal zero unless there is a charge associated with the compound +5 2 +5 6

Oxidation Numbers Common Oxidation States of Nonmetals Pg. 235

Oxidation Numbers Oxidation Numbers for Formulas and Names Many nonmetals can have more than one oxidation number These numbers can sometimes be used in the same manner as ionic charges to determine formulas (+ -) What is the formula of a binary compound formed between sulfur and oxygen? From the +4, +6 oxidation numbers of sulfur, you could predict that sulfur might form SO2 or SO3 Remember: The more-electronegative element in a binary compound is assigned a negative number equal to the charge it would have as an anion. Likewise for the less-electronegative element.

Oxidation Numbers Oxidation Numbers for Formulas and Names Using oxidation numbers, the Stock system, introduced in the previous section for naming ionic compounds, can be used as an alternative to the prefix system for naming binary molecular compounds Prefix system Stock system PCl3 phosphorus trichloride phosphorus(III) chloride PCl5 phosphorus pentachloride phosphorus(V) chloride N2O dinitrogen monoxide nitrogen(I) oxide NO nitrogen monoxide nitrogen(II) oxide Mo2O3 dimolybdenum trioxide molybdenum(III) oxide

Practice Problems Assign oxidation numbers to each atom in the following compounds or ions: HF CI4 H2O PI3 CS2 Na2O2 H2CO3 NO2ˉ