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Ionic and Covalent Compounds

Ionic and Covalent Compounds. 5.1 Compounds 5.2 Lewis Dot Symbols 5.3 Ionic Compounds and Bonding 5.4 Naming Ions and Ionic Compounds 5.5 Covalent Bonding and Molecules 5.6 Naming Molecular Compounds 5.7 Covalent Bonding in Ionic Species 5.8 Molecular and Formula Masses

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Ionic and Covalent Compounds

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  1. Ionic and Covalent Compounds 5.1 Compounds 5.2 Lewis Dot Symbols 5.3 Ionic Compounds and Bonding 5.4 Naming Ions and Ionic Compounds 5.5 Covalent Bonding and Molecules 5.6 Naming Molecular Compounds 5.7 Covalent Bonding in Ionic Species 5.8 Molecular and Formula Masses 5.9 Percent Composition of Compounds 5.10 Molar Mass 5

  2. Lewis Dot Symbols Lewis dot symbols of the main group elements represent the valence electrons in the atom. •• • • N • • 1s22s22p1 1s22s22p2 1s22s22p3 •• • • • • • • • • 5 valence electrons; first pair formed in the Lewis dot symbol B C O •• For nonmetals in the second period, the number of unpaired dots is the number of bonds the atom can form.

  3. Lewis Dot Symbols Na+ Na 1s22s22p63s1 •• •• Na+ 1s22s22p6 • • • • • O Na O 2‒ Na • •• •• •• O O2‒ 1s22s22p6 •• For main group metals such as Na, the number of dots is the number of electrons that are lost forming the cation. • • • • For nonmetals in the second period, the number of unpaired dots also represents the # of electrons needed to form the common anion which will have a complete octet. O 1s22s22p4

  4. Lewis Dot Symbols Lewis dot symbols of the main group elements represent the valence electrons in the atom. 1 2 3 4 5 6 7 8 s1 s2 s2 p1 s2 p3 s2 p5 s2 p2s2 p4 s2 p6

  5. N3- O2- F- Ne Na+ Mg2+ 1s2 2s2 2p6 B 1s2 2s2 2p1 C 1s2 2s2 2p2 N O F Ne Na Mg 1s2 2s2 2p6 1s2 2s2 2p6 1s2 2s2 2p3 1s2 2s2 2p6 1s2 2s2 2p4 [Ne] 3s0 1s2 2s2 2p5 [Ne] 3s0 1s2 2s2 2p6 All the ions shown are ‘isoelectronic’ to Neon Period 2/3 electron configurations Ion - electron configurations [Ne] 3s1 [Ne] 3s2

  6. Compounds Molecular compounds – nonmetal + nonmetal e.g H2O or CH4 Ionic compounds – metal + nonmetal e.g. NaCl or CaBr2 Formula - # of atoms of each element in a compound Empirical Formula – simplest whole number ratio of elements in a compound. (Ionic cpds or molecules)

  7. +1 none +2 -2 -1 -3 +3 variable ion formation Main Group ions are isoelectronic to inert gases

  8. Ionic Compounds Metal’s keeps element name (Roman Numerals) used for cations with multiple ion charges Nonmetal’s ending changed to -ide

  9. Ionic Compounds - formulas 1. Metal first then nonmetal 2. Nonmetal’s ending changed to -ide • Net charge (empirical formula) = 0 • don’t indicate numbers Sodium chloride NaCl Aluminum oxide Sodium oxide A. Al3O2 A. NaO B. Na2O B. AlO3 C. NaO2 C. AlO D. NaOH D. Al2O3

  10. Ionic Compounds - naming 1. Metal first – say metal’s name 2. Nonmetal’s ending changed to -ide 3. Do not indicate numbers CaBr2 A. Calcium dibromine K2S B. Calcium dibromide C. Calcium bromide A. potassium sulfide D. Calcium bromate B. potassium sulfite C. potassium sulfate D. dipotassium sulfate

  11. Ionic Compounds – transition metals CuCl vs. CuCl2 Copper (I) chloride vs. copper (II) chloride • Manganese (II) nitride • Mn2N • Mn2N3 • Mn3N2 • MnN2 • Iron (II) oxide • Fe2O3 • FeO • Fe2O • FeO2 • MnBr5 • manganese (V) bromide • magnesium (II) bromide • manganese bromide • manganese pentabromide

  12. Review – Ionic cpds – formulas and naming You need to know charges on main group ions given periodic table Naming: metal first then nonmetal with ‘ide’ do not use numeric prefixes to indicate amts. (this is because all charges are known) with TMs say + charge after name followed by nonmetal Formulas: metal symbol first then nonmetal symbol use subscript numerals to indicate correct empirical formula. (they are always the same because the charges are fixed) with TMs put + charge of metal in ( ) following symbol

  13. Ionic Compounds Formulas for ionic compounds are generally empirical formulas. There is no unique unit of an ionic compound. e.g. NaCl not Na6Cl6 etc. The formulas must reflect that ionic compounds are electronically neutral.

  14. Q1×Q2 d2 Ionic Compounds and Bonding F α A three-dimensional array of oppositely-charged ions is called a lattice. Lattice energy is the amount of energy required to convert a mole of ionic solid to its constituent ions in the gas phase. NaCl(s)  Na+(g) + Cl−(g) Hlattice = +788 kJ/mol − − − − − − − + + + + + + +

  15. Compounds Molecular compounds – nonmetal + nonmetal e.g H2O or CH4 Formula - # of atoms of each element in a compound Empirical Formula – simplest whole number ratio of elements in a compound. (Ionic cpds or molecules) Molecular Formula – exact # of atoms of each element in smallest unit of substance (molecules only) empirical molecular Benzene: CH vs. C6H6 Hydrogen peroxide: HO vs. H2O2

  16. Molecular Compounds - naming 1. More positive element 1st – say name 2. More electronegative last using -ide 3. Indicate numbers with prefix (mono typically excluded for 1st element) CO = carbon monoxide CO2 = carbon dioxide CCl4 = carbon tetrachloride N2O4 = dinitrogentetroxide BrF5= ?????

  17. Common names of molecular compounds (p. 63) H2O = water not dihydrogen oxide CH4 = methane not carbon tetrahydride NH3 = ammonia not nitrogen trihydride H2S = hydrogen sulfide not dihydrogen sulfide

  18. Compounds Containing Hydrogen A compound must contain at least one ionizable hydrogen atomto be an acid upon dissolving.

  19. What is the name of …. N2O • Nitrogen oxide • Oxygen dinitride • dinitrogen oxide • Nitrogen (II) oxide • What is the name of …. Mn2O3 • Manganese (II) Oxide • Manganese Oxide • Manganese (III) trioxide • Manganese (III) oxide • What is the formula for sodium sulfide? • NaS b) NaS2 c) Na2S2 d) Na2S

  20. Polyatomic Ions(know these names) Behaves as nonmetal Cations OH- hydroxide CO32- carbonate HCO3- bicarbonate NO3- nitrate NO2- nitrite SO42-sulfateHSO4- hydrogen sulfate SO32-sulfite HSO3- hydrogen sulfite CH3COO- acetate PO43-phosphate HPO42- hydrogen phosphate and H2PO4- dihydrogen phosphate CN- cyanide ClO4- perchlorate ClO- hypochlorite NH4+ammonium H3O+ hydronium These collections of nonmetal atoms form covalent bonds within the ion, but form ionic compounds with metals (or ammonium with nonmetals)

  21. Polyatomic Ions Behaves as nonmetal Behaves as metal OH- hydroxide CO32- carbonate HCO3- bicarbonate NO3- nitrate NO2- nitrite SO42-sulfateHSO4- hydrogen sulfate SO32-sulfite HSO3- hydrogen sulfite CH3COO- acetate PO43-phosphate HPO42- hydrogen phosphate and H2PO4- dihydrogen phosphate CN- cyanide NH4+ ammonium (NH4)2SO4 = ammonium sulfate • Mn(NO3)2= • Manganese (II) dinitrate • Manganese (II) nitrite • Manganese (II) nitrate • Dimanganese nitrate • Na2CO3 • disodium carbonate • Sodium bicarbonate • disodium tricarbonate • Sodium carbonate e.g. KOH = potassium hydroxide Do not confuse …. sulfide, sulfate, sulfite nitride, nitrate, nitrite etc.

  22. Compounds Containing Hydrogen A compound must contain at least one ionizable hydrogen atomto be an acid upon dissolving. Acids that contain complex ions e.g. H2SO4 HNO3 HClO4 H2CO3 are named by changing the complex ion ending to “ic” followed by acid Other acid names ……. H2SO3 = sulfurous acid HNO2 nitrous acid

  23. A hydrate is a compound that has a specific number of water molecules within its solid structure. Systematic name: copper(II) sulfate pentahydrate Formula: Cu(SO)4 ∙ 5H2O Some other hydrates are BaCl2 ∙ 2H2O LiCl ∙ H2O MgSO4 ∙ 7H2O Sr(NO3)2 ∙ 4H2O Anhydrousmeans the compound no longer has water molecules associated with it. Cu(SO)4∙5H2O(s) + heat → Cu(SO)4(s) + 5H2O(g)

  24. Formula Weight (FW) & Molecular Weight (MW) Formula weight applies to anything with a formula: atoms, ionic compounds, and molecular compounds. Atomic weight (AW) and Molecular weight apply to atoms/molecules only. FW = Sum of AWs of all atoms in compound. Cu(SO4) • 5H2O FW = ?? What is the MW of H2SO4 (sulfuric acid). MW = 2 • 1.0079 + 32.065 + 4 • 15.999 = 98.077 g/mol Ca3(PO4)2 = 309.963 g/mol What is the FW of calcium phosphate?

  25. % composition (by weight) Ca3(PO4)2 = 309.963 g/mol Represent the % of each element in the compound based on weight. % composition = __Mass of element__ • 100 mass of compound % Ca = __3 • 40.078 __ • 100 = 38.8 % 309.963 % P = __2 • 30.974 __ • 100 = 20.0 % 309.963 % 0 = __8 • 15.999 __ • 100 = 41.3 % 309.963 sum = 100.1%

  26. What is the FW of Ni(NO3)2? AW: Ni = 58.7 N = 14.01 O = 16.00 a) 62.0 b) 120.7 c) 182.7 d) 241.4 units = g/mol FW Ni(NO3)2 = 58.7 + 2 • 14.0 + 6 • 16.0 = 182.7 g/mol What is the % (by wt) of Ni in Ni(NO3)2? AW Ni (58.7)x 100 = 32.1% FW Ni(NO3)2(182.7) • 11 • 32 • 46 • 62

  27. Finding the formula from the % composition by weight • Assume 100g of compound A compound contains 38.8% Ca, 20.0% P, and 41.3% O. What is it’s empirical formula? 2. Mass  AW = # mol repeat for each atom 3.  # mol by lowest # 4. Simplest whole # ratio = empirical formula • If MW is known a molecular formula can be determined

  28. A compound is composed of 41.6 % Mg (AW = 24.3) 54.9 % O (AW = 16.0) 3.4 % H (AW = 1.01) What is its empirical formula? Name the compound. Determine its FW. a) MgOH2 b) MgO2H2 c) Mg2OH2d) MgO2H2 round to whole #s 1 2 2 41.7 g Mg 54.9 g O 3.4 g H ÷ 24.3 g mol-1 ÷ 16.0 g mol-1 ÷ 1.01 g mol-1 = 1.72 = 3.43 = 3.4 ÷ 1.72 = 1.00 ÷ 1.72 = 1.99 ÷ 1.72 = 1.98 MgO2H2

  29. Formula Weight & Molecular Weight % composition (by weight) Empirical formula vs. Molecular formula Empirical formula from % composition

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