Ionic Bonding Chapter 20

A. Ionic Bonds Attraction between 2 oppositely charged ions Ions - charged atoms caused by gain or loss of electrons formed by transferring e- from a metal to a nonmetal

A. Ionic Bonds Cations (metals) first, anions written second (nonmetals or polyatomic ions) Do NOT share electrons, one gains, and one loses

B. Ionic Compounds Network of ions, NOT a molecule When melted or dissolved in water, ionic compounds conduct electricity Ions are free to move, electric current is moving charges

C. Comparison Chart IONIC COVALENT transferred from metal to nonmetal shared between nonmetals Electrons Melting Point high low Soluble in Water yes usually not yes (solution or liquid) Conduct Electricity no crystal lattice of ions, crystalline solids molecules, odorous liquids & gases Other Properties

Naming Ionic Compounds Oxidation Number Ionic Names Ionic Formulas Ch. 20 - Ionic Bonds Naming Ionic Compounds Oxidation Number Ionic Names Ionic Formulas

A. Oxidation Number The charge on an ion Indicates the # of e- gained/lost to become stable 1+ 2+ 3+ 4± 3- 2- 1-

B. Ionic Names For binary ionic compounds (2 elements) Write the names of both elements, cation first Change the anion’s ending to –ide NO PREFIXES!! NaCl = sodium chloride CaCl2 = calcium chloride

B. Ionic Names NaBr Na2O AlCl3 sodium bromide sodium oxide aluminum chloride

C. Ionic Formulas Write each ion including the oxidation number Cation is written first Oxidation numbers are written as superscripts Overall charge must equal zero If charges cancel, just write the symbols If not, crisscross the charges to find subscripts

C. Ionic Formulas Calcium chloride Ca2+ Cl1- charges do not cancel, must criss-cross charges Rewrite as complete formula without oxidation numbers CaCl2 1 2

C. Ionic Formulas potassium chloride magnesium nitride calcium oxide K+ Cl-  KCl Mg2+ N3-  Mg3N2 Ca2+ O2-  CaO

D. Polyatomic Ions A group of bonded atoms that have gained or lost e- List on chart – need to know these for Quiz on Tuesday!!! Parentheses are put around these when naming – (NH4)2SO4 = ammonium sulfate

D. Polyatomic Ions Naming compounds with PA ions: For ionic compounds with more than 2 elements Write the names of both ions, cation first Write the full names of polyatomic ions (usually anion) – do not change the names

E. Ionic Formulas with PA Ions calcium hydroxide aluminum chlorate magnesium carbonate Ca2+ OH-  Ca(OH)2 Al3+ ClO3-  Al(ClO3)3 Mg2+ CO32-  MgCO3

E. Ionic Formula with PA ions Write each ion including the oxidation number Cation is written first Overall charge must equal zero If charges cancel, just write the symbols If not, crisscross the charges to find subscripts Use parentheses when more than one polyatomic ion is needed

E. Ionic Formulas with PA Ions calcium hydroxide aluminum chlorate magnesium carbonate Ca2+ OH-  Ca(OH)2 Al3+ ClO3-  Al(ClO3)3 Mg2+ CO32-  MgCO3

F. Ionic Compounds with Transition Metals For transition metals, valence electrons and oxidation #’s are variable Exceptions: Sn (tin), Pb (lead), Ag1+, and Zn2+ Roman numerals indicate the oxidation # Chromium (III) = Cr3+ Iron (II) = Fe2+ Lead (IV) = Pb4+

G. Ionic Formulas with Transition Metals Copper (II) bromide Tin (IV) oxide Manganese (II) chloride Cu2+ + Br -  CuBr2 Sn4+ + O2-  Sn2O4  SnO2 Mn2+ + Cl -  MnCl2

H. Naming Ionic Compounds with Transition Metals Write the ox. # in parentheses using Roman numerals. To determine oxidation #, know that overall charge of compound = 0 Cr2O3 CrO 3 x -2 = -6 2 x ___ = +6 Chromium (III) oxide -3 Formula: Element: # atoms x charge = total charge 2 x -2 = -4 2 x ___ = +4 Chromium (II) oxide +2

H. Naming Ionic Compounds with Transition Metals Shortcut that sometimes works – criss-cross backwards CrCl2  Cr Cl2 chromium (II) chloride 2 1

I. Ionic Names with Transition Metals Cr2(SO4)3 HgO FeCl3 Chromium (III) sulfate Mercury (II) oxide iron(III) chloride