Ionic Compounds Chapter 8. Remember…. Chemical bond Electron-dot structure Ionization energy Electron affinity – how much attraction an atom has for electrons.

Ionic CompoundsIonic CompoundsChapter 8

Remember….Remember….Chemical bondElectron-dot structureIonization energyElectron affinity – how much

attraction an atom has for electrons

ElectronegativityOctet ruleCation Anion

Atoms in contact will Atoms in contact will interact!interact!Based on electronegativity

difference:◦1.8-3.3 ionic (metals with nonmetals)◦0.4-1.7 polar covalent (varying

degrees)◦0.0-0.3 nonpolar covalent (2

nonmetals)◦ See page 169

What about metals with other metals?

Metallic atoms share their valence Metallic atoms share their valence electrons freely in a “sea of electrons” electrons freely in a “sea of electrons” to form to form alloysalloys..

BrassWhite gold14K goldSteelCast ironBronzePewter

Cu + ZnAu + Ni or PdAu + Cu or AgFe + CFe + C + SiCu + SnSn + Cu or Sb or

Pb

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Properties of other Properties of other bonding:bonding: Ionic

◦ Crystalline arrangement (brittle/will shatter)

◦ High melting and boiling temperatures

◦ Ratio of atoms involved is determined by charges

◦ Non-conductive unless molten, dissolved in water

Covalent◦ Molecular

arrangement◦ Lower melting and

boiling temperatures (may even be gases!)

◦ Ratio of atoms involved is determined experimentally

◦ Generally non-conductive

Ionic BondIonic BondElectrostatic force that holds

oppositely charged particles together in an ionic compound

Binary ionic compounds – contain only two different elements◦A metallic cation and a nonmetallic

anionElectrolyte – ionic compound

whose aqueous solution conducts an electric current

Ionic BondIonic Bond# electrons lost must = #

electrons gained◦Calcium: 2+ charge◦Fluorine: 1- charge◦1 Ca to every 2 F: CaF2

Example Ionic BondExample Ionic BondSodium chlorideNa+1 , Cl-1 Methods: (p. 216)

◦Electron configuration◦Orbital notation◦Electron-dot structures◦Atomic models

Energy and Ionic BondsEnergy and Ionic Bonds

Endothermic – energy absorbed during a chemical reaction

Exothermic – energy released during a chemical reaction◦Ionic compounds always exothermic

reaction

Energy and Ionic BondsEnergy and Ionic BondsLattice energy – energy required

to separate one mole of ions of an ionic compound◦Reflects strength of forces holding

ions together ◦More negative lattice energy,

stronger force of attraction

Crystal strength:Crystal strength:Determined by ionic radius

◦Smaller radii = higher lattice energy

Determined by ionic charge◦Higher charge = higher lattice

energy

KI < KF < LiF < MgO

Predicting ionic ratiosPredicting ionic ratiosBased on charge ratios (“formula

units” – simplest ratio of the ions)Cations first, anions secondFor example

◦Na 1+ and Cl 1- ; therefore, will combine 1:1 NaCl “sodium chloride”

◦Na 1+ and S 2-; therefore, will combine 2:1 Na2S “sodium sulfide”

◦Be 2+ and N 3-; therefore, will combine 3:2 Be3N2 “beryllium nitride”

Oxidation NumberOxidation NumberCharge of a monatomic ion (one-

atom ion)Also known as oxidation stateGroup 1: +1Group 2: +2

D-block cationsD-block cationsHave varying oxidation numbersCharges of these elements are

indicated with Roman numerals (Stock method) ◦Cu (I) or Cu (II)

OR name changes (less common)◦“-ic” means higher option (cupric =

2+)◦“-ous” means lower option (cuprous

= 1+)

Naming Binary Ionic Naming Binary Ionic CompoundsCompoundsName the cation (including

charge if a d-block metal) and the anion with “-ide”

Sodium chloride Gold (III) iodideBeryllium oxide Zinc nitride

Polyatomic ionsPolyatomic ionsA group of atoms acting as one

cation or anion◦Memorize the chart on page 224 (Table

8.6)◦Yes, all of it—test next Thursday

If more than one needed – parenthesis◦Mg(ClO3)2

Oxyanions- negatively charged polyatomic ion containing oxygen

Make another ‘A’Make another ‘A’VocabularyMemorize polyatomic ionsRead about alloysRead about properties of ionic

compoundsPractice writing formulas and

names

Covalent bondingCovalent bonding…not ‘til next chapter! ;0)

The end!