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While Lewis Structures were covered in regular chem, they are very important in organic chem, and get modified slightly. First, watch this video to review basic Lewis structures.
Lets practice some basics Lewis Structures. Grab a piece of paper and a pencil and sketch out this list of molecules, and state their strongest IMF. Include lone pairs. NH3 CH4 CH2O C6H14 [OH]- C2H3N
Scroll to reveal the correct diagrams.
If you want more practice with Lewis Structures, here is a worksheet from chemteam. Feel free to do as many or as few as you would like.
Compounds made of Hydrogen and Carbon are creatively named hydrocarbons. There is special nomenclature for these, dependent on the amount of carbon atoms. For the first few, the Lewis structures are very easy. However, as more carbons are added on, these structures begin to take a while to draw. To avoid spending 5 minutes sketching out a molecule with 20 Hydrogens and 10 Carbons, chemists began omitting the C's and H's to simplfy. To take it a step further, the lines to the Hydrogens were also left out, and are now just assumed to be attached at corners. To review this, take a look at a drawing of Hexene using these new rules.
Each corner is assumed to be a carbon atom, with 2 attached hydrogen atoms, and three on each end. Since organic chemistry deals with carbon, being able to simplify its Lewis structures is very useful. These simplified structures are called line structures. When drawing these structures, be sure to count the corners, not line segments, to find the total number of carbon atoms.
An offshoot of hydrocarbons are cyclical hydrocarbons. Instead of being lines, these molecules join both ends together to form shapes. These too can be drawn without carbons and hydrogens labeled. Since the ends of these structures have been joined together, there is no longer free electrons to attach the extra hydrogens onto the end. Therefore, the formula for cyclohexane is C6H12, instead of hexane's normal C6H14. The rule for cyclical hydrocarbons is very easy, as the number of hydrogen atoms will be twice that of the carbon atoms.
Shorting Lewis structures through this method goes much further than just hydrocarbons. This video expands a little on what we have gone through already in the lesson, covering skeletal structures and more complicated line structures. Use the image below to see a summary of how to simplify structures.
Have you mastered Lewis Structures? Take the quiz to find out!
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