Presentation on theme: "Lewis Dot Diagrams Show where electrons and bonds exist in covalent compounds. [http://www.bbc.co.uk/schools/gcsebitesize/img/gcsechem_54.gif]"— Presentation transcript:
Lewis Dot Diagrams Show where electrons and bonds exist in covalent compounds. [http://www.bbc.co.uk/schools/gcsebitesize/img/gcsechem_54.gif]
Lewis Dot Diagrams Dots are used to show valence electrons for specific atoms. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-02.2un.JPG]
Lewis Dot Diagrams Electrons are “shared” to form bonds and satisfy the octet rule. Example: H 2 O [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-19un.JPG]
Lewis Dot Diagrams Example: NH 3 1 st – Count up all valence electrons N = 5 e - H = 1 e - x 3 = 3 e - 8 total valence electrons
Lewis Dot Diagrams 2 nd – Draw individual dot diagrams Hint – place 1 per side to start. N HHH
Lewis Dot Diagrams 3 rd – Connect lone electrons to satisfy octet rule and form “bonds” Remember, H only wants 2 e - ! N H H H
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. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_10/FG10_00-71un.JPG] 8 Total Electrons!
Lewis Dot Diagrams Some compounds will share more than 2 electrons, so multiple bonds are drawn. Example: O 2
Each O has 8 e - Double Bond
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]
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]
Lewis Dot Diagrams Too many valence electrons Si not stable Center H has too many e - N not stable What is wrong in the following diagrams?