1. Covalent Bonding

2. Electrons are shared between two nonmetals Weaker attractive force than ionic bonding

3. Properties of Molecular Compounds State at SATPTypically gases & liquids, but some solids StructureVariable (waxy to brittle) Melting & Boiling PointsLow Electrical ConductivityNonelectrolyte Solubility in WaterVariable (low to high)

4. Covalent Bonding Formation of hydrogen chloride: H  + Cl    Cl  H  H - Cl  Covalent bond, shared electrons Lone pairs, valence electrons not involved in covalent bond Structural Formula: H-Cl (lone pairs are not drawn)

5. Polyatomic Ions Many compounds contain a combination of covalent and ionic bonds. E.g. NaOH OH - is a polyatomic ion with a covalent bond between O and H Ionic bond between Na + and OH -

6. Lewis Structures H   H +  Cl  Cl  H2:H2: or H H Cl 2 : Cl   Cl   + or Cl Cl   H H Structural Formula: Cl-Cl

7. Double and Triple Bonds Atoms can share 4 electrons to form a double bond or 6 electrons to form a triple bond. The number of shared electron pairs (covalent bonds) that an atom can form is the bonding capacity. O2:O2: N2:N2: = O  N 

8. Coordinate Covalent Bonds A covalent bond in which both of the shared electrons come from the same atom. e.g. NH 3 (ammonia) and H + (hydrogen ion) to form NH 4 (ammonium)

9. Drawing Lewis Structures 1.Arrange the element symbols. Central atoms are generally those with the highest bonding capacity. Carbon atoms are always central atoms Hydrogen atoms and halogen atoms are always peripheral atoms 2.Add up the number of valence electrons from all atoms. For polyatomic ions, add one electron for each negative charge and subtract one for each positive charge. 3.Draw a skeleton structure with atoms attached by single bonds. 4.Complete the octets of peripheral atoms. 5.Place extra electrons on the central atom. 6.If the central atom doesn’t have an octet, try forming multiple bonds by moving lone pairs.

10. SAMPLE PROBLEMWriting Lewis Structures for Molecules with One Central Atom PROBLEM:Write a Lewis structure for CCl 2 F 2, one of the compounds responsible for the depletion of stratospheric ozone.

11. Draw Lewis structures for: HF H2OH2O NH 3 CH 4 H F  or H F  H O H  or H O H  H N H H  or H N H H  H C H H H  or H C H H H

12. SAMPLE PROBLEMWriting Lewis Structure for Molecules with More than One Central Atom PROBLEM:Write the Lewis structure for methanol (molecular formula CH 4 O), an important industrial alcohol that is being used as a gasoline alternative in car engines.

13. SAMPLE PROBLEMWriting Lewis Structures for Molecules with Multiple Bonds. PROBLEM:Write Lewis structures for the following: (a) Ethylene (C 2 H 4 ), the most important reactant in the manufacture of polymers (b) Nitrogen (N 2 ), the most abundant atmospheric gas

14. Drawing Lewis Structures – more practice COCl 2 HOCl ClO 3  24 e- 14 e- 26 e-  Cl C Cl O  H O Cl  O Cl O O  

15. Practice Problems p.79 #2 p. 80 #3 p. 81 #5, 6, 9,13 - 15