1. Chapter 811 Chapter 8 Basic Concepts of Chemical Bonding CHEMISTRY The Central Science 9th Edition

2. Chapter 821 Chemical bond: attractive force holding two or more atoms together Covalent bond: electrons are shared Usually found between nonmetals Ionic bond results from the transfer of electrons from a metal to a nonmetal Metallic bond: attractive force holding pure metals together 8.1: Chemical Bonds, Lewis Symbols, and the Octet Rule

3. Chapter 831 Text, P. 277 Valence electrons are represented as dots around the symbol for the element Electrons available for bonding are indicated by unpaired dots

4. Chapter 841 The Octet Rule All noble gases except He have an ns 2 np 6 configuration Octet rule: atoms tend to gain, lose, or share electrons until they are surrounded by 8 valence electrons (4 electron pairs)

5. Chapter 851 Consider the reaction between sodium and chlorine: Na(s) + ½Cl 2 (g)  NaCl(s)  Hº f = -410.9 kJ 8.2: Ionic Bonding

6. Chapter 861 NaCl forms a very regular structure Regular arrangement of Na + and Cl - in 3D Ions are packed as closely as possible

7. Chapter 871 Energetics of Ionic Bond Formation Lattice energy: the energy required to completely separate an ionic solid into its gaseous ions NaCl (s)  Na + (g) + Cl - (g) is endothermic (  H = +788 kJ/mol) Lattice energy depends on the charges on the ions and the sizes of the ions

8. Chapter 881 Lattice energy (and thus stability) increases as The charges on the ions increase The distance between the ions decreases High lattice energies make ionic compounds hard and brittle with high melting points

9. Text, P. 279

10. Chapter 8101 8.3: Covalent Bonding When two similar atoms bond, neither of them wants to lose or gain an electron to form an octet Similar electron affinities They share pairs of electrons to each obtain an octet Example: H + H  H 2

11. Chapter 8111 Lewis Structures Covalent bonds can be represented by the Lewis symbols of the elements: In Lewis structures, each pair of electrons in a bond is represented by a single line:

12. Chapter 8121 Multiple Bonds It is possible for more than one pair of electrons to be shared between two atoms (multiple bonds): One shared pair of electrons = single bond Two shared pairs = double bond Three shared pairs = triple bond Bond distances decrease from single  triple bonds