CHAPTER 15 OUTLINE
IONIC BONDING AND IONIC COMPOUNDS
I. Electron Configuration in Ionic Bonding
     A.
Valence electrons --> electrons in the highest occupied energy level (outer shell electrons)
          1. only electrons involved in bonding
          2. determine chemical properties of elements
          3. related to group # and electron configurations
          4.
Electron dot structure --> shows valence electrons as dots
               a. Inner shell electrons and nucleus represented as elements symbol
     B. electron Configurations for cations
          1.
Octet rule --> in forming compounds, atoms tend to achieve the electron config. of noble gases (8 electrons in outer shell)
               a. Gilbert Lewis, 1916
          2. Loss of valence electrons produces a cation (positive ion)
               a. Leave an octet in the next lowest energy level
                    Na     1s2,2s2,2p6,3s1 (losses one electron)
                    Na+     1s2,2s2,2p6 (same as Ne)
               b. Na+ and Mg+2 both have the same configuration as Ne
                    Na --> Na+ + e-
                    Mg --> Mg+2 + 2e-
               c. Metals lose enough electrons to get config. of a noble gas
          3. Transition metals have multiple charges
               a. make
pseudo noble-gas configs.
               b. filled sublevels, not necessarily energy levels
     C. electron Configurations for anions
          1. Gain of valence electrons produce an anion (negative ion)
               a. Gains on octet in the outer energy level
                    F     1s2,2s2,2p5 (gains one electron)
                    F-     1s2,2s2,2p6 (same as Ne)
               b. O-2 and F- both have the same configuration as Ne
                    F + e- --> F-
                    O + 2e- --> O-2
               c. Nonmetals gain enough electrons to get config. of a noble gas
                    1.
When halogens gain one electron, the ion is called a halide ion
II. Ionic bonds
     A. Formation of Ionic Compounds
          1.
Ionic Bond -- electrstatic force that binds oppositely charged ions together
               a.
Ionic Compounds -- neutral compounds made by ionic bonds
          2. Metals give electrons to nonmetals so each can form noble gas configs.
               a. Form cations and anions
                    Ex. sodium chloride --> Na & Cl -->  Na+ & Cl-
               b. Chemical formula is simple whole # ratio between cations and anions --> NaCl
     B. Properties of Ionic Compounds
          1.
Most ionic compounds are crystalline structures
               a.
3-d repeating arrangements
                    1. each cation is surrounded by anions
                    2. each anion is surrounded by cations
               b. Maximize attractive forces, minimize repulsive forces in crystalline arrangement
               c. Very stable structure with high melting points
          2.
Coordinate number --> # of ions of opposite charge that surround a ion in the crystal
               a. Ex. --> NaCl (each Na is surrounded by 6 Cl and each Cl is surrounded by 6 Na)
                    1. Na & Cl both have a coordinate # of 6
          3. Determine internal structure of crystals using
X-ray diffraction crystallography
          4. ionic compounds conduct electricity when melted or dissolved (
Electrolyte)
               a. Ions are free to move around
               b.
Cations move towards negative electrode (cathode)
               c.
Anions move towards positive electrode (anode)
III. Bonding in Metals
     A. Metallic bonds and Metallic Properties
          1.
Metals are closely packed cations surrounded by moving valence electrons
               a.
Metallic bond --> attraction between free-flowing valence electrons and the cation
           2. Properties of metals are based on this fact
               a. Good conductors of electricity
               b.
Ductile - drawn (pulled) into wire
               c.
Malleable - bend into shapes
                    1. cations role by each other like ball bearings in oil (the electrons)
                    2. Remember ionic compound shatter!
     B. Crystalline Structure of Metals
          1.
Body-centered cubic --> every atom has 8 neighbors (Ex. - Na, K, Fe, Ch, & W)
          2.
Face-centered cubic --> every atom has 12 neighbors (Ex. - Cu, Ag, Au, Al & Pb)
          3.
Hexagonal close-packed --> every atom has 12 neighbors (Ex. - Mg, Zn, Cd)
     C.
Alloys --> mixtures of two or more elements with at least one being a metal
          1. Their properties are usually better than the metals that make up the alloy
               a. Ex. --> Steel, sterling silver, stainless steel, brass, bronze
               b. Steel is made out of iron, carbon, boron, chromium, manganese, molybdenum, nickel, tungsten, and vanadium
          3. two types of Alloys
               a.
Substitutional alloy --> where atoms of the same size replace each other in the crystalline structure
               b.
Interstitial alloy --> where smaller atoms fill in spaces between larger atoms in the crystalline structure


Outline based upon:
     Matta, M. S., Staley, D. D., Waterman, E. L., & Wilbraham, A. C. (2
000). Chemistry, Addison-Wesley. (5th ed.). Menlo Park, CA: Prentice Hall, pp. 413-430.


                                                        
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