IONIC BONDING An electrical attraction between two oppositely charged atoms or groups of atoms. Happens when an atom of a nonmetal takes one or more electrons from an atom of a metal so both atoms end up with eight valence electrons The Octet Rule • The octet rule says that atoms can become stable by having eight electrons in their outer energy level, as shown in the noble gas, Neon, (or two electrons in the case of some of the smallest atoms). Electron Dots For Cations Metals will have few valence electrons These will come off Ca Electron Dots For Cations Metals will have few valence electrons These will come off Forming positive ions 2+ Ca Electron Dots For Anions Nonmetals will have many valence electrons. They will gain electrons to fill outer shell. P 3P IONIC COMPOUNDS metal with nonmetal + ion - ion Ca+ion anion Predicting Oxidation Number or Charge from Periodic Table Forming Cations metals group 1A group 2A group 3A group 4A lose elose 1 lose 2 lose 3 lose 4 form cations +1 charge +2 charge +3 charge +4 charge oxidation # 1+ 2+ 3+ 4+ Forming Anions Non-metals gain e- group 7A group 6A group 5A gain 1 gain 2 gain 3 form anions -1 charge -2 charge -3 charge oxidation # 123- +1 1 H 2 Li 3 4 5 6 7 11 0 +2 +3 +4 -3 -2 -1 Be B C N O F 12 Na Mg 13 +3 19 20 21 22 23 24 K Ca Sc Ti V Cr Mn Fe Co Ni 37 38 39 Rb Sr Y 55 56 71 40 76 45 77 Cs Ba La Hf Ta W Re Os Ir 87 88 103 104 Fr Ra Ac Rf 105 106 107 108 109 46 17 18 Si P S Cl Ar Cu Zn Ga Ge As Se Br Kr 29 30 +2 Al 31 32 35 36 48 +2 49 79 80 81 82 83 84 Pt Au Hg Ti Pb Bi Po At Rn Db Sg Bh Hs Mt Oxidation Numbers 51 34 47 +1 78 50 33 I 75 44 28 16 Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te 74 43 27 15 53 73 42 26 N 14 52 72 41 25 He 85 54 Xe 86 IONIC BONDING Neutral atoms come near each other. Electron(s) are transferred from the Metal atom to the Non-metal atom. They stick together because of electrostatic forces, like magnets. Steps for writing ionic bond formulas 1. Determine the oxidation numbers for the two elements or ions. Ca = +2, Cl = -1 Steps for writing ionic bond formulas 2. Write the chemical symbols in the correct order, with the metal ion first and write the oxidation numbers as superscripts. Ca 2+ Cl -1 Steps for writing ionic bond formulas 3. Crisscross the numbers only—not the charge signs—writing the oxidation number of one element as a subscript for the other. Don’t write number 1 either. Ca 2+ Cl 1Ca 1 Cl 2 Ca Cl2 Steps for writing ionic bond formulas 4. Determine whether the formula is in its simplest form. Reduce the subscripts to the simplest from by dividing by a common denominator. Ca+2 O-2 Ca2 O2 CaO = Ca2O2 Steps for writing ionic bond formulas 5. Check the formula by calculating the total positive and negative charges and confirming that the total charge on the compound is zero. CaCl 2 Oxidation Number Subscript Calcium (+2) x (1) = +2 Chlorine (-) x (2) = -2 Practice these! magnesium and oxygen aluminum and bromine sodium and sulfur potassium and nitrogen MgO AlBr3 Na2S K3N More Practice! potassium bromide calcium oxide Silver fluoride KBr CaO AgF Polyatomic ions Groups of atoms that stick together as a unit, and have a charge PO43- phosphate CO32- carbonate C2H3O41- acetate Names often end in –ate or –ite Steps for writing ionic bond formulas 6. POLYATOMIC IONS ACT JUST LIKE ANY OTHER NEGATIVE ION WHEN BONDING Treat polyatomic ion as single unit— don’t change it in any way! Steps for writing ionic bond formulas Steps for writing ionic bond formulas polyatomic ions are enclosed in parenthesis if taken more than once in the formula. A subscript outside the parenthesis multiplies everything inside. Steps for writing ionic bond formulas Practice potassium hydroxide KOH zinc (II) carbonate ZnCO3 barium chlorate Ba(ClO3)2 aluminum phosphate AlPO4 More Practice calcium acetate Ca(C2H3O2) 2 sodium nitrate NaNO3 aluminum hydroxide Al(OH) 3 ammonium phosphate (NH4)3 PO4 Naming Ionic Compounds 1. name cation - then anion 2. if anion (nonmetal) is a single element ….. then name ends in “-ide” Naming Ionic Compounds 3. If metal have more than one possible charge (include roman numeral in parenthesis to give charge)* *All metals except: Ag+1, Zn+2, Cd+2, Al+3 Practice (no transitional metals) Na2O Sodium oxide Mg(OH)2 Manganese (II) oxide Al(NO3)3 Aluminum nitrate NH4Cl Ammonium chloride Practice with transitional metals Hint: look at the subscript in the anion to predict the metal oxidation number. Sn(ClO3)4 Tin(IV) chlorate Cu2CO3 Copper (I) carbonate Fe2O3 Iron (III) oxide NiSO4 Nickel (II) sulfate Properties of Ionic Compounds Crystalline structure. A regular repeating arrangement of ions in the solid. Ions are strongly bonded. Structure is rigid. High melting points- because of strong forces between ions. Crystalline structure The repeating unit is called the unit cell 3 dimension Crystalline structure The POSITIVE CATIONS stick to the NEGATIVE ANIONS, like a magnet. + + - - + + + - + - + - + - + Ionic solids are brittle + + - + + + + - + + Ionic solids are brittle Strong Repulsion breaks crystal apart. - + - + + - + - + - + Cubic Body-Centered Cubic Face-Centered Cubic Do they Conduct? Conducting electricity is allowing charges to move. In a solid, the ions are locked in place. Ionic solids are insulators. When melted, the ions can move around. Melted ionic compounds conduct. First get them to 800ºC. Dissolved in water they conduct.