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Unit 8: Ionic Bonds. Chapter 8 Chemistry 1L Cypress Creek High School. Part 2: Naming and Writing Formulas for Ionic Compounds. Sodium and chlorine bond in a 1:1 ratio to form NaCl Calcium and chlorine bond in a 1:2 ratio for form CaCl 2
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Unit 8: Ionic Bonds Chapter 8 Chemistry 1L Cypress Creek High School
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? ________________ Ionic Bonds – Writing Formulas oxidation numbers
Ionic Bonds – Writing Formulas 2+2- Al & Cl AlCl3 3+1- Ca & S Ca2S2 CaS • 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
Try to predict the ratio and resulting formula for each of the following ions based on their oxidation numbers: Ionic Bonds – Writing Formulas Li2S 2:1 Li+ & S2- Al3+ & O2- Al2O3 2:3 3:1 Na+ & P3- 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
We’ve already predicted these formulas. Now, try to predict the names for each binary salt: Binary Salt Naming lithium sulfide aluminum oxide sodium phosphide barium fluoride
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
Ternary Salt Formulas + 3- Al & SO3 Al2(SO3)3 3+2- K & PO4 K3PO4 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.
Try to predict the formulas and names for each ternary salt: calcium carbonate CaCO3 1:1 Ca2+ & CO32- barium nitrate Ba(NO3)2 2:1 Ba2+ & NO3- sodium phosphate Na3PO4 Na+ & PO43- 1:3 ammonium sulfide 1:2 (NH4)2S NH4+ & S2- Ternary Salt Formulas & Naming
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
cobalt (III) hydroxide nickel (II) phosphate lead (IV) oxide chromium (II) sulfide Co(OH)3 Ni3(PO4)2 PbO2 CrS 1:1 2:3 2:1 3:1 Cr2+ & S2- Co3+ & OH- Ni2+ & PO43- Pb4+ & O2- Salts with Multiple Oxidation Numbers Practice