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Ch 8 ionic compounds


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Ch 8 ionic compounds

  1. 1. IONIC COMPOUNDS Chapter 8
  2. 2. Forming Chemical Bonds Section 8.1 <ul><li>The force that holds two atoms together is called a chemical bond. </li></ul><ul><li>Chemical bonds may form by the attraction between a positive nucleus and negative electrons or the attraction between a positive ion and a negative ion </li></ul>
  3. 3. Review… <ul><li>Valence electrons are the electrons in the outermost energy level. These same electrons are involved in the formation of chemical bonds between two atoms </li></ul>
  4. 4. Electron-Dot Structures Especially useful when illustrating formation of chemical bonds!!
  5. 5. From Chapter 6… <ul><li>Ionization energy refers to how easily an atom loses an electron. </li></ul><ul><ul><li>Noble gases, having high ionization energies, show a general lack of chemical reactivity </li></ul></ul><ul><ul><li>The difference in reactivity is directly related to the valence electrons </li></ul></ul><ul><ul><li>Elements tend to react to acquire the stable electron structure of a noble gas (V.E. 8) </li></ul></ul>
  6. 6. From Ch 6 <ul><li>Electronegativity – ability to attract e- in a chemical bond. </li></ul><ul><li>The greater electronegativity difference as that b/w a metal and a nonmetal = Ionic Bond </li></ul><ul><li>Ionic Bond – Eneg difference above 1.7 </li></ul><ul><ul><li>** Elements farther from each other </li></ul></ul><ul><ul><li>Refer to table pg 169 of textbook </li></ul></ul>
  7. 7. Formation of Positive Ions <ul><li>A positive ion forms when an atom loses one or more valence electrons in order to attain a noble gas configuration </li></ul>Positively charged ion is called a cation
  8. 8. Transition Metals <ul><li>When forming positive ions, transition metals commonly lose their valence electrons, forming 2+ ions. </li></ul><ul><ul><li>However, it is also possible for d electrons to be lost </li></ul></ul><ul><li>A useful rule of thumb for these metals is that they form ions with a 2+ or 3+ charge. </li></ul>
  9. 9. Formation of Negative Ions <ul><li>Nonmetals have a great attraction for electrons and form stable outer electron configuration by gaining electrons </li></ul>Negatively charged ion is called an anion
  10. 10. Checkpoint <ul><li>Why do ions form? </li></ul><ul><li>Describe the formation of positive and negative ions. </li></ul><ul><li>Predict the change that must occur to achieve noble gas stability </li></ul><ul><ul><li>Nitrogen </li></ul></ul><ul><ul><li>Sulfur </li></ul></ul><ul><ul><li>Barium </li></ul></ul><ul><ul><li>Lithium </li></ul></ul>
  11. 11. Answers <ul><li>Atoms gain stability by losing or gaining electrons </li></ul><ul><li>Positive ions form when atoms lose valence electrons </li></ul><ul><ul><li>Negative ions form when valence electrons are added to an atom </li></ul></ul><ul><li>Nitrogen- gain 3 electrons (N 3- ) </li></ul><ul><li>Sulfur- gain 2 electrons (S 2- ) </li></ul><ul><li>Barium- lose 2 electrons (Ba 2+ ) </li></ul><ul><li>Lithium- lose 1 electron (Li 1+ ) </li></ul>
  12. 12. CW <ul><li>P.214 #1-5 </li></ul><ul><li>P.236 #47-50, 60-66 </li></ul>
  13. 13. The Formation and Nature of Ionic Bonds (Section 8.2) <ul><li>The electrostatic force that holds oppositely charged particles together in an ionic compound is referred to as an ionic bond </li></ul><ul><li>Ionic bonds form between cations (+) and anions (-) </li></ul><ul><li>Binary compounds contain two different elements </li></ul><ul><ul><li>Metallic cation </li></ul></ul><ul><ul><li>Nonmetallic anion </li></ul></ul>Electrons gained = electrons lost OVERALL CHARGE OF THE COMPOUND FORMED MUST BE ZERO!!!
  14. 14. Properties of Ionic Compounds <ul><li>High Melting and boiling points (indicating strong bond strength b/w ions with greater positive and negative charge ) </li></ul><ul><li>Most are crystalline solids at room temperature </li></ul><ul><li>ions in a regular, geometric pattern (crystal lattice) </li></ul><ul><li>hard, brittle </li></ul><ul><li>conduct electricity when molten or dissolved in water (aka electrolyte ) </li></ul>
  15. 15. Homework <ul><li>P.220 #12-18 </li></ul><ul><li>P.236 #53,67-73 </li></ul><ul><li>Lattice structure of various elements and compounds </li></ul><ul><li>Diamond lattice structure vs Graphite </li></ul>
  16. 16. Names and Formulas for Ionic Compounds (Very Important!) Section 8.3 <ul><li>Terms to be familiar with: </li></ul><ul><ul><li>Formula Unit- the simplest ratio of the ions represented in an ionic compound </li></ul></ul><ul><ul><li>Monatomic Ion- a one-atom ion (Mg 2+ or Br 1- ) </li></ul></ul><ul><ul><li>Oxidation Number- the charge of the monatomic ion </li></ul></ul><ul><ul><li>Polyatomic Ion- ions made up of more than one atom (i.e. Nitrate= NO 2 - ) </li></ul></ul>
  17. 17. Predicting ionic ratios <ul><li>Based on charge ratios (“formula units” – simplest ratio of the ions) </li></ul><ul><li>Cations first, anions second </li></ul><ul><li>For example </li></ul><ul><ul><li>Na 1+ and Cl 1- ; therefore, will combine 1:1 </li></ul></ul><ul><ul><ul><li>NaCl “sodium chloride” </li></ul></ul></ul><ul><ul><li>Na 1+ and S 2-; therefore, will combine 2:1 </li></ul></ul><ul><ul><ul><li>Na 2 S “sodium sulfide” </li></ul></ul></ul><ul><ul><li>Be 2+ and N 3-; therefore, will combine 3:2 </li></ul></ul><ul><ul><ul><li>Be 3 N 2 “beryllium nitride” </li></ul></ul></ul>
  18. 18. Write the correct formula for the ionic compound composed of the following pairs of ions <ul><li>Potassium and iodine </li></ul><ul><li>Magnesium and chlorine </li></ul><ul><li>Aluminum and bromide </li></ul><ul><li>Cesium and nitride </li></ul>
  19. 19. Answers <ul><li>1. Potassium and iodine </li></ul><ul><li>K +1 and I -1  KI (1:1 ratio) </li></ul><ul><li>2. Magnesium and chlorine </li></ul><ul><li> Mg +2 and Cl -1  MgCl 2 (1:2 ratio) </li></ul><ul><li>3. Aluminum and bromide </li></ul><ul><li> Al +3 and Br -1  AlBr 3 (1:3 ratio) </li></ul><ul><li>4. Cesium and nitride </li></ul><ul><li> Cs +1 and N -3  Cs 3 N (3:1 ratio) </li></ul>
  20. 20. Compounds Containing Polyatomic Ions <ul><li>The charge given to a polyatomic ion applies to the entire group of atoms </li></ul><ul><li>The polyatomic ion acts as an individual ion </li></ul><ul><li>NEVER CHANGE THE SUBSCRIPTS WITHIN THE ION </li></ul><ul><li>If more than one polyatomic ion is needed, place parentheses around the ion and write the appropriate subscript outside the parentheses. </li></ul>
  21. 21. Practice Problems <ul><li>Calcium and Nitrate </li></ul><ul><li>Aluminum and Hydroxide </li></ul><ul><li>Barium and Sulfate </li></ul><ul><li>Sodium and Phosphate </li></ul><ul><li>Potassium and Sulfate </li></ul>
  22. 24. Naming Ionic Compounds <ul><li>Oxyanion - a polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms </li></ul><ul><ul><li>An ion with more oxygen atoms is named using the root of the nonmetal plus the suffix –ate (ex. NO 3 -  nitr ate ) </li></ul></ul><ul><ul><li>An ion with fewer oxygen atoms is named using the root of the nonmetal plus the suffix –ite (ex. NO 2 -  nitr ite ) </li></ul></ul>
  23. 25. Chlorine’s 4 Oxyanions <ul><li>ClO 4 -  per chlor ate (most oxygen's) </li></ul><ul><li>ClO 3 -  chlor ate (one less oxygen) </li></ul><ul><li>ClO 2 -  chlor ite (two fewer oxygen's) </li></ul><ul><li>ClO -  hypo chlor ite (three fewer oxygen's) </li></ul>
  24. 26. Naming Ionic Compounds <ul><li>Name the cation (+) first and the anion (-) second. </li></ul><ul><li>Monatomic cations use the element name. </li></ul><ul><li>Monatomic anions take their element name plus the suffix –ide . </li></ul>
  25. 27. <ul><li>4. Transition metals (d-block cations) often have more than one oxidation number. </li></ul><ul><ul><li>The oxidation number is written as a Roman numeral in parentheses after the name of the cation </li></ul></ul><ul><li>5. If the compound contains a polyatomic ion, simply name the ion. </li></ul>
  26. 28. Practice problems <ul><li>NaBr </li></ul><ul><li>CaCl 2 </li></ul><ul><li>KOH </li></ul><ul><li>Cu(NO 3 ) 2 </li></ul><ul><li>Ag 2 CrO 4 </li></ul>
  27. 29. Cation + Anion <ul><li>Na Br  sodium bromide </li></ul><ul><li>Ca Cl 2  calcium chloride </li></ul><ul><li>K OH  potassium hydroxide </li></ul><ul><li>Cu ( NO 3 ) 2  copper (II) nitrate </li></ul><ul><li>Ag 2 CrO 4  silver chromate </li></ul>
  28. 30. Writing a Chemical Formula from the Name <ul><li>Step 1: Write the element symbol(s) for name of the ion(s). </li></ul><ul><li>Step 2: Write the charge of the ion(s). </li></ul><ul><li>Step 3: If the total charge equals zero, you are done. If the total charge does not equal zero, you must change the subscripts so that the total charge equals zero (‘drop-n-cross’). </li></ul>
  29. 31. Section Review Anion  Cation  Oxide Chloride Sulfate Phosphate Potassium Barium Aluminum Ammonium
  30. 32. Answers Anion  Cation  Oxide Chloride Sulfate Phosphate Potassium K 2 O KCl K 2 SO 4 K 3 PO 4 Barium BaO BaCl 2 BaSO 4 Ba 3 (PO 4 ) 2 Aluminum Al 2 O 3 AlCl 3 Al 2 (SO 4 ) 3 AlPO 4 Ammonium (NH 4 ) 2 O NH 4 Cl (NH 4 ) 2 SO 4 (NH 4 ) 3 PO 4
  31. 33. Homework <ul><li>P.227 #35-36,38-39 </li></ul><ul><li>P.237 #74-79 </li></ul>
  32. 34. Metallic Bonds and Properties of Metals (Section 8.4) <ul><li>Although metals do not bond ionically, they often form lattices in the solid state. </li></ul><ul><li>Electron sea model- all the metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons </li></ul>
  33. 35. <ul><li>The electrons present in the outer energy levels of the bonding metallic ions are not held by any specific atom and can move easily from one atom to the next. (Delocalized electrons) </li></ul><ul><li>A metallic bond is the attraction of a metallic cation for delocalized electrons </li></ul>
  34. 36. Metal Characteristics <ul><li>Moderately high melting points but high boiling points </li></ul><ul><ul><li>vary greatly but not as extreme as boiling point </li></ul></ul><ul><li>Soft, malleable, and ductile </li></ul><ul><li>Shiny </li></ul><ul><ul><li>Delocalized e- absorb and release photons of light </li></ul></ul><ul><li>Good conductors of electricity </li></ul>
  35. 37. Metal Alloys <ul><li>A mixture of elements that has metallic properties </li></ul><ul><ul><li>Substitutional - atoms of the original metallic solid are replaced by other metal atoms of similar size </li></ul></ul><ul><ul><ul><li>Brass, pewter, 10-carat gold, and sterling silver </li></ul></ul></ul><ul><ul><li>Interstitial- formed when small holes in a metallic crystal are filled with smaller atoms </li></ul></ul><ul><ul><ul><li>Carbon steel </li></ul></ul></ul>
  36. 38. Alloys Brass: zinc + copper Pewter: 90% Tin + Bi, Sb, Cu, Pb 10 carat gold: 10 part gold + 14 part alloy of copper & Ag Sterling silver: silver + copper (Ge, Zn, Pt)
  37. 39. Homework <ul><li>P.237 #80-82,84 </li></ul>
  38. 40. Bibliography <ul><li> </li></ul><ul><li>Clear Science </li></ul><ul><ul><li> </li></ul></ul>