2Remember…. Chemical bond Electron-dot structure Ionization energy Electron affinity – how much attraction an atom has for electronsElectronegativityOctet ruleCationAnion
3Atoms in contact will interact! Based on electronegativity difference:ionic (metals with nonmetals)polar covalent (varying degrees)nonpolar covalent (2 nonmetals)See page 169What about metals with other metals?
4Metallic atoms share their valence electrons freely in a “sea of electrons” to form alloys. BrassWhite gold14K goldSteelCast ironBronzePewterCu + ZnAu + Ni or PdAu + Cu or AgFe + CFe + C + SiCu + SnSn + Cu or Sb or Pb
6Properties of other bonding: IonicCrystalline arrangement (brittle/will shatter)High melting and boiling temperaturesRatio of atoms involved is determined by chargesNon-conductive unless molten, dissolved in waterCovalentMolecular arrangementLower melting and boiling temperatures (may even be gases!)Ratio of atoms involved is determined experimentallyGenerally non-conductive
7Ionic BondElectrostatic force that holds oppositely charged particles together in an ionic compoundBinary ionic compounds – contain only two different elementsA metallic cation and a nonmetallic anionElectrolyte – ionic compound whose aqueous solution conducts an electric current
8Ionic Bond # electrons lost must = # electrons gained Calcium: 2+ chargeFluorine: 1- charge1 Ca to every 2 F: CaF2
9Example Ionic Bond Sodium chloride Na+1 , Cl-1 Methods: (p. 216) Electron configurationOrbital notationElectron-dot structuresAtomic models
10Energy and Ionic BondsEndothermic – energy absorbed during a chemical reactionExothermic – energy released during a chemical reactionIonic compounds always exothermic reaction
11Energy and Ionic BondsLattice energy – energy required to separate one mole of ions of an ionic compoundReflects strength of forces holding ions togetherMore negative lattice energy, stronger force of attraction
13Predicting ionic ratios Based on charge ratios (“formula units” – simplest ratio of the ions)Cations first, anions secondFor exampleNa 1+ and Cl 1- ; therefore, will combine 1:1NaCl “sodium chloride”Na 1+ and S 2-; therefore, will combine 2:1Na2S “sodium sulfide”Be 2+ and N 3-; therefore, will combine 3:2Be3N2 “beryllium nitride”
14Oxidation Number Charge of a monatomic ion (one-atom ion) Also known as oxidation stateGroup 1: +1Group 2: +2
15D-block cations Have varying oxidation numbers Charges 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+)
16Naming Binary Ionic Compounds Name the cation (including charge if a d- block metal) and the anion with “-ide”Sodium chloride Gold (III) iodideBeryllium oxide Zinc nitride
17Polyatomic ions A group of atoms acting as one cation or anion Memorize the chart on page 224 (Table 8.6)Yes, all of it—test next ThursdayIf more than one needed – parenthesisMg(ClO3)2Oxyanions- negatively charged polyatomic ion containing oxygen
18Make another ‘A’ Vocabulary Memorize polyatomic ions Read about alloys Read about properties of ionic compoundsPractice writing formulas and names
19Covalent bonding…not ‘til next chapter! ;0)The end!