Chapter 8 Chemistry 1L Cypress Creek High School Unit 8: Ionic Bonds Chapter 8 Chemistry 1L Cypress Creek High School

Part 2: Naming and Writing Formulas for Ionic Compounds

Ionic Bonds – Writing Formulas Sodium and chlorine bond in a 1:1 ratio to form NaCl Calcium and chlorine bond in a 1:2 ratio for form CaCl2 What determines each ratio & formula? ________________ oxidation numbers

Ionic Bonds – Writing Formulas CRISS-CROSS METHOD Oxidation numbers (excluding charge) of each ion trade places to become the subscripts in the formula – must be reduced to lowest whole number ratio; 1’s are not written Ca & S Ca2S2 Al & Cl AlCl3 3+ 1- 2+ 2- CaS 4

Ionic Bonds – Writing Formulas Try to predict the ratio and resulting formula for each of the following ions based on their oxidation numbers: Ions Oxidation Numbers Ratio Formula Magnesium & Oxygen Mg2+ & O2- 1:1 MgO Lithium & Sulfur Aluminum & Oxygen Sodium & Phosphorus Barium & Fluorine Li+ & S2- 2:1 Li2S Al3+ & O2- 2:3 Al2O3 Na+ & P3- 3:1 Na3P Ba2+ & F- 1:2 BaF2

Three Types of Ionic Compounds We will learn how to write nomenclature for: Binary Salts 2 elements: a metal and a nonmetal Ternary Salts 3 or more elements Includes a polyatomic ion Salts with Multiple Oxidation Numbers Can be binary or ternary Includes a transition metal

Binary Salt Naming Contains 2 elements: cation & anion Naming: Name the cation (no changes) Drop the end of anion and add “ide” Example: MgCl2 = magnesium chloride

Binary Salt Naming We’ve already predicted these formulas. Now, try to predict the names for each binary salt: Ions Oxidation Numbers Ratio Formula Name Magnesium & Oxygen Mg2+ & O2- 1:1 MgO magnesium oxide Lithium & Sulfur Li+ & S2- 2:1 Li2S Aluminum & Oxygen Al3+ & O2- 2:3 Al2O3 Sodium & Phosphorus Na+ & P3- 3:1 Na3P Barium & Fluorine Ba2+ & F- 1:2 BaF2 lithium sulfide aluminum oxide sodium phosphide barium fluoride

Name Formula acetate C2H3O2- or CH3COO- ammonium NH4+ carbonate CO32- chlorate ClO3- chlorite ClO2- chromate CrO42- cyanide CN- dichromate Cr2O72- hydrogen carbonate HCO3- hydroxide OH- hypochlorite ClO- nitrate NO3- nitrite NO2- perchlorate ClO4- permanganate MnO4- phosphate PO43- sulfate SO42- sulfite SO32- Polyatomic Ions Some ions contain more than one element - called a polyatomic ion The group as a whole has an overall charge Examples: Lithium and sulfate would bond together to make Li2SO4 Ammonium and sulfur would bond together to make (NH4)2S

Ternary Salt Naming Contains 3 or more elements: cation & anion – most polyatomic ions are anions, only cation is ammonium (NH4+) Naming: Name the cation (no changes) Name the anion (no changes) Example: Na2SO4 = sodium sulfate Exception: When ammonium is paired with an element anion NH4Cl = ammonium chloride

Al & SO3 Al2(SO3)3 K & PO4 K3PO4 Ternary Salt Formulas You must use parentheses if you have more than one polyatomic ion. Be sure to criss-cross the oxidation numbers and write it OUTSIDE of the parentheses. + 3- Al & SO3 Al2(SO3)3 3+ 2- K & PO4 K3PO4 11

Ternary Salt Formulas & Naming Try to predict the formulas and names for each ternary salt: Ions Oxidation Numbers Ratio Formula Name Potassium & Hydroxide K+ & OH- 1:1 KOH potassium hydroxide Calcium & Carbonate Barium & Nitrate Sodium & Phosphate Ammonium & Sulfur Ca2+ & CO32- 1:1 CaCO3 calcium carbonate Ba2+ & NO3- 2:1 Ba(NO3)2 barium nitrate Na3PO4 Na+ & PO43- 1:3 sodium phosphate NH4+ & S2- 1:2 (NH4)2S ammonium sulfide

Salts with Multiple Oxidation #s Naming Transition elements can form more than one type of positive ion. For example, copper can form both Cu+ and Cu2+ ions, and iron can form both Fe2+ and Fe3+ ions. Zinc and silver are two exceptions – they only have one oxidation number The zinc ion is Zn2+ and the silver ion is Ag+. Naming: Name the cation Put the roman numeral representing the oxidation # of the metal in parentheses (do not indicate the charge) Name the anion, changing the ending to “ide” (binary) or naming the polyatomic ion (ternary) Example: FeCl2 = iron (II) chloride FeCl3 = iron (III) chloride

Salts with Multiple Oxidation Numbers Practice Ions Oxidation Numbers Ratio Formula Name Copper & Nitrate Cu+ & NO3- 1:1 CuNO3 copper (I) nitrate Lead & Oxygen Cobalt & Hydroxide Nickel & Phosphate Chromium & Sulfur Pb4+ & O2- 2:1 PbO2 lead (IV) oxide Co3+ & OH- 3:1 Co(OH)3 cobalt (III) hydroxide Ni2+ & PO43- 2:3 Ni3(PO4)2 nickel (II) phosphate Cr2+ & S2- 1:1 CrS chromium (II) sulfide