1. Chemical Bonding Chapter 6

2. Chemical Bond Chemical Bond – an attraction between atoms to hold the atoms together

3. Review Which type of elements are the most stable (least willing to undergo change)? How many valence electrons do they have? What would you expect of the other elements to increase their stability?

4. Octet Rule Octet Rule- atoms gain, lose, or share electrons in order to acquire a full set of 8 valence electrons. We will address exceptions to octet rule also. Ex. sodium A sodium ion is more stable than the neutral sodium atom because it now has 8 valence electrons.

5. 3 types of Bonds Nonpolar covalent bonds- valence electrons are shared equally between bonded atoms. Polar covalent bonds- valence electrons are shared unequally between the bonded atoms. Ionic bonds- valence electrons are transferred from one atom to another forming ions. These oppositely charged ions attract.

6. Bonding between atoms is rarely purely ionic or covalent. It is usually some degree between the two. General rule on the type of bond that forms between two atoms: Ionic bond-a metal and a nonmetal, or a polyatomic Covalent bond-2 or more non-metals, sharing of electrons

7. Electronegativity Electronegativity Differences-Used to determine what type of bond forms (Pg. 151) 0-.2 nonpolar covalent.3-1.7 polar covalent >1.7 ionic Example: Determine the type of bond with electronegativity differences: H and Cl:Cs and Cl:Cl and Cl: Prac p163 and section review p163

8. Molecular Cmpds Molecule (2 or more nonmetals)-a neutral group of atoms held together by covalent bonds Molecular cmpd Molecular formula-shows the number and kind of atoms in a molecule of a compound Diatomic molecule-molecule with only 2 atoms Ex. Diatomic elements-element that comes as 2 atoms (Memorize:HBrONClIF)

9. Diagram graph on p165, show why a bond forms at position c and not at d, a. Show the overlapping of orbitals in H 2

10. Chemical Bonds Bond Length – distance between 2 bonded atoms Bond energy – energy required to break a chemical bond into isolated atoms

11. Electron Dot Notation Electron Dot Notation – Element symbol represent the nucleus and electrons other than the valence electrons. The dot (s) around the symbol represent the valence electrons Note: This is an important representation because it is mostly the valence electrons that undergo chemical rxns

12. Illustrate the electron dot notation for all the elements in period 2:

13. Lewis Structures Lewis structures-using electron dot notation to show the way atoms form a compound

14. Single Bond Single bond is the sharing of one pair of electrons between 2 atoms, represented by 2 elec dots or a dash. Ex. H 2 HF

15. Single Bond Draw these Lewis structures. Note if C is in the formula, it is the central atom. H 2 O, HBr, F 2, NH 3, H 2 S, CH 3 I

16. Double Bond Double bond – covalent bond formed by sharing two pairs of electrons b/t atoms. Illustrate C 2 H 4, CO 2

17. Triple Bond Triple bond-a covalent bond formed by sharing 3 lone pairs of electrons between two atoms. Illustrate C 2 H 2, N 2

18. Multiple Bonds Double bonds and triple bonds are called multiple bonds. Which type of bond is the strongest? p173 Weakest? Which bond is the longest? Shortest? Practice 174

19. Resonance Resonance – bonding that requires several structures to represent the molecule or ion. The actual molecule (ion) is resonating from one structure to another. Ex. O 3, CO 3 -2 Section Review p175

20. Ionic Bond Ionic cmpd – cmpd made up of positive and negative ions that combine to be neutral. Formula unit – simplest repeating unit of ionic cmpd

21. Formation of Ionic Cmpd Using electron dot structure Ex. Na and Cl to Na + and Cl - = NaCl Ex. Ca and F to Ca +2 and F -1 = CaF 2 Section Review p180

22. Ionic vs. Molecular Cmpds 1.Ionic cmpds have very strong attractions to hold the formula units together. Attractions holding molecules together is weaker. 2.Ionic cmpds have high melting pt, boiling pt, and high degree of hardness due to above reason. 3. Ionic cmpds are brittle. Illustrate reason. See p179 fig. 6-17

23. Polyatomic Ions Polyatomic Ions – group of atoms bonded covalently that have a charge. Suffix of –ate, if more oxygens Suffix of –ite, if less oxygens

24. Metallic Bonding Metallic Bonding – bonding due to attraction between metal atoms and a sea of electrons. Illustrate concept. Malleability – metals can be hammered into sheets Ductility – metals can be drawn into wires Section Review p182

25. Molecular Geometry VSEPR Theory = valence shell electron pair repulsion theory = valence pairs stay as far as possible from each other due to repulsion. Illustrate and name the 8 different molecular shapes to be memorized (p186) Practice p187

26. Hybridization Hybridization – mixing of 2 or more atomic orbitals to produce new orbitals of the same energy Ex. Illustrate:

27. Polar vs. Nonpolar molecules To determine if a molecule is polar or nonpolar: 1. Identify the shape of molecule 2. Show bond polarity with aid of electronegativity Ex. HCl, CO 2, CH 4, NH 3, H 2 O

28. Intermolecular Forces Intermolecular Forces – attractions between molecules 3 types 1. Dipole-Dipole – attraction between polar molecules Ex. Show dipole-dipole force between two molecules of NH 3

29. 2. Hydrogen Bonding – intermolecular force where hydrogen is attracted to an unshared pairs of electrons on another molecule Illustrate with NH 3 and H 2 O 3. London Dispersion Forces – temporary intermolecular attractions caused by motion of molecules. Illustrate with H 2 and O 2 Section Review p193

30. Polymers Polymers – large molecules made up of many units joined through rxns Monomers – small units Thermoplastic polymer – melts when heated and can be reshaped many times Thermosetting polymer – doesn’t melt when heated but keeps its original shape

31. Types of Polymers There are linear polymers, branched polymers, and cross linked polymers. See diagram p685

32. Types of Polymers Addition Polymer – formed from double bonded monomers linked up. Ex. CH 2 =CH 2 CH 2 =CH 2 CH 2 =CH 2 → -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 - Condensation Polymer – formed by removing a molecule of water between two monomers See p690 for example

33. Patterns of Monomers Possible Patterns of monomers: AAAAAA ABABAB AAABBBAAABBB AABBBBBBABAA