CHAPTER 5.1 IONIC COMPOUNDS IONIC COMPOUNDS • • • • • • Charged ions with neutral cpd. Water soluble Metal with non metal Brittle Electric conductor Tightly bound repeating patterns in crystals • Cation: + charged ion • Anion: - charged ion Types of Ionic Compounds I. Binary Ionic Compounds • only contains 2 elements (can have more than one ion of each element) - Bi – Latin for “2” Ex: NaCl sodium chloride - charges cancel each other - compound is neutral - do not write charges of ions in formula - 1:1 ratio of each element Binary Ionic Compounds ex: CaFl2 calcium flouride (1:2 ratio) AlCl3 aluminum chloride (1:3 ratio) K2S potassium sulfide (2:1 ratio) Naming Binary Ionic Compounds Rules 1. Write name of metal ( + cation) 2. Write name of non metal (- anion) 3. Change non metal name to end in “ide” (number of each element does not change name) Name the following binary compounds: Mg2O3 magnesium oxide KCl potassium chloride Na2S sodium sulfide LiI lithium iodide TiBr titanium bromide Writing Formulas Rules 1. If more than one ion of an element is present, the subscript tells how many 2. Write subscript below and to the right of element (sub-below) 3. Write the formula unit (simplest ratio of elements) Ex: FORMULA UNIT CaF2 NaCl Ga2S3 REPEATING PATTERN Ca2F4 Ca3F6 Na2Cl2 Na6Cl6 Ga4S6 Ga8S12 Write the formula units for the following: Rb2F2 RbF Mg3Cl9 MgCl3 Al6O18 AlO3 C12H24O12 CH2O H4S2O8 H2SO4 Writing Binary Ionic Formulas Rules 1. Write the symbol for the metal then the non-metal 2. Determine the oxidation number of each element (use periodic table) oxidation number: charge on ion (superscript) - tells number of electrons atom gains or loses Oxidation Numbers Metals: - always have + charge (lose negative electrons) - charge equals group # on periodic tbl. (remove 1 in front of group 13) Oxidation Numbers Non metals: - always have – charge (gain negative electrons) - charge equals 8 minus group # (remove 1 in front of groups 15, 16, 17, 18) 3. Rewrite formula so compound is neutral (positive and negative charges must be equal) 2+ – ex: Mg Br Are the charges equal? In order for the compound to be neutral we must have equal positive and negative charges. CRISS-CROSS RULE 1. take number of metal’s superscript (number above element) 2. move this number to bottom right of non-metal symbol (now a subscript, loses charge) 3. do the same for the non-metal Criss Cross Rule Ex: Mg Br Mg 2+ Br - Mg1 Br2 Final Formula (do not write charges on subscripts) Mg Br2 charges are equal, compound is neutral Mg has 2+ charges x one atom = 2+ charges Br has 1- charge x two atoms = 2- charges II. Polyatomic Compounds compound that contains more than two elements • Polyatomic Ion: Ion that has two or more different elements in a grouped unit which carries a charge a. whole ion is charged, not last element listed b. treated same as single element’s (monoatomic) ion ex: ammonium cyanide + NH4 CN polyatomic polyatomic ion ion c. can contain: 1. one (+) metal bonded to (–) polyatomic ion + Na OH - metal nonmetal 2. (+) polyatomic ion bonded to one (-) non metal ion + - NH4 I polyatomic nonmetal ion 3. (+) polyatomic ion bonded to a (-) polyatomic ion + - NH4 NO3 polyatomic polyatomic Naming Polyatomic Compounds Rules 1. name + ion first, followed by name of – polyatomic ion 2. do not change ending of – polyatomic ion ex: CaCO3 calcium carbonate Name the following polyatomic compounds: (use reference sheet) LiNO2 lithium nitrate NaCN sodium cyanide MgSO4 magnesium sulfate AlSO3 aluminum sulfite CaPO4 calcium phosphate KNO3 potassium nitrate NaOH sodium hydroxide MgCr2O7 magnesium dichromate * H3OCl hydronium chloride * NH4I ammonium iodide * Remember to change non metal’s name to “ide” Writing Polyatomic Formulas Rules 1. Use criss-cross method ammonium nitride NH4+ N3- 2. Put parenthesis around polyatomic ion 3. Criss-cross superscript to bottom right of parenthesis around polyatomic ion (NH4) 3 N1 hydronium phosphide H3O + P2(H3O)2P Practice Problems III. Transition Element Compounds (groups 3-12) a. form + ions like metals b. can have more than one type of + ion (have more than 1 oxidation number) c. named by using name of element followed by oxidation number as Roman numeral in parenthesis ex: Cu(I)Cl Cu(II)Cl copper I chloride copper II chloride IV. Hydrates ionic compound that contains H2O molecules weakly bound in its crystals - when hydrates lose their water, the end compound has different properties than the original hydrate ex: popcorn kernel yellow, hard cobalt chloride (anhydrous) cement gel popped corn white, soft cobalt chloride (hydrate) cement hardened Hygroscopic substances: Ionic compounds that easily become hydrates (absorb H2O) The thorny devil features hygroscopic grooves between the spines of their skin to capture water in their desert habitat. Deliquescent substances: Substance that absorbs so much water it becomes liquid salts Dessicants: Absorb water vapor and keeps surrounding substance dry silica gel packs inside electronics Anhydrous compound: Hydrate with all water removed anhydrous sodium sulfate Naming Hydrates Rules 1. Write the name of the compound 2. Write the prefix of the number of water molecules 3. Add the word “hydrate” to the prefix ex: Ba(NO3)2 . 4 H2O barium nitrite tetrahydrate Prefixes for Naming Compounds Number Prefix 1 Mono- 2 Di- 3 Tri- 4 Tetra- 5 Penta- 6 Hexa- 7 Hepta- 8 Octa- 9 Nona- 10 Deca- Name the following hydrates: CaSO4 . 3 H2O NaSO4 . 4 H2O . 6 H2O NiNo3 . 7 H2O NaOH . 9 H2O FeO2 LiPO4 . 10 H2O . 5 H2O MgCr2O7 . H2O AlSO3 KCl BaOH . 2 H2O . 8 H2O Writing Hydrate Formulas Rules 1. Write the formula for the compound (must be neutralized) 2. Place a dot after formula 3. Write the number of water molecules ex: copper sulfate dihydrate CuSO4 . 2 H2O sodium carbonate pentahydrate Na2CO3 . 5 H2O Write the formulas for the following hydrates: Beryllium sulfite pentahydrate Cesium chloride trihydrate Copper (I) phosphate decahydrate Barium oxide octahydrate Calcium hydroxide dihydrate Scandium (II) bromide trihydrate Sodium carbonate nonahydrate Potassium sulfide heptahydrate Radium flouride hexahydrate Ammonium cyanide monohydrate Study for the test !