Lewis Dot Diagrams

1. Lewis Dot Diagrams • Show where electrons and bonds exist in covalent compounds. [http://www.bbc.co.uk/schools/gcsebitesize/img/gcsechem_54.gif]

2. Lewis Dot Diagrams • Dots are used to show valenceelectrons for specific atoms. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-02.2un.JPG]

3. Lewis Dot Diagrams • Electrons are “shared” to form bonds and satisfy the octet rule. • Example: H2O [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-19un.JPG]

4. Lewis Dot Diagrams • Example: NH3 • 1st – Count up all valence electrons • N = 5 e- • H = 1 e- x 3 = 3 e- • 8 total valence electrons

5. Lewis Dot Diagrams • 2nd – Draw individual dot diagrams • Hint – place 1 per side to start. N H H H

6. Lewis Dot Diagrams • 3rd – Connect lone electrons to satisfy octet rule and form “bonds” • Remember, H only wants 2 e- ! N H H H

7. Lewis Dot Diagrams • Last Step – Draw a “final” picture with lines (2 shared electrons) • Make sure that all valence electrons are accounted for! • Any electrons that are not in bonds are called unshared, or lone pairs. 8 Total Electrons! [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-71un.JPG]

8. Lewis Dot Diagrams • Some compounds will share more than 2 electrons, so multiple bonds are drawn. • Example: O2

10. Double Bond Each O has 8 e-

11. Lewis Dot Diagrams • Exceptions to the Octet Rule: • Boron (6 e-) [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-46un.JPG]

12. Lewis Dot Diagrams • Phosphorus (10 e-) • Sulfur (12 e-) [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-46un.JPG]

13. Lewis Dot Diagrams What is wrong in the following diagrams? Too many valence electrons Si not stable Center H has too many e- N not stable