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Lewis Dot Diagrams |
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* When first looking at a Lewis Dot Diagram, most students are somewhat perplexed. Before them is the periodic symbol of an element surrounded by a bunch of dots. This is what some Lewis Dot Diagrams for atoms look like:
* In Fordham Prep’s chemistry course, Lewis Dot Diagrams are drawn for atoms, molecules, and ionic compounds. The rules for molecules and atoms are identical, but rules for drawing Lewis Dot Diagrams for molecular compounds are slightly more complicated.
Atoms & Molecules
1) The symbol of an element is used to represent its nucleus and everything else, save its outer electrons.
2) The first step in drawing a Lewis Dot Diagram is determining the look of the element’s outer electrons. For this task, one must figure out the element’s electron configuration.
3) From an element’s electron configuration, it is possible to identify the electrons in the outer energy level.
4) Every symbol has four sides (top, bottom, left, right). Every side represents an orbital and every orbital can hold up to two electrons. Dots are drawn on appropriate sides representing the electrons in the orbitals.
5) The greatest number of electrons that can be depicted in a Lewis Dot Diagram is eight. Only two of these electrons, those in the "S" orbital, are paired together. This means that they will always be drawn on the same side, although which side that is does not matter.
6) All other electrons are to be distributed as equally as possible around the symbol. This means that there can never be two electrons, other than "S" electrons, on one side while another side is empty.
Molecular Compounds
* Lewis Dot Diagrams for molecular compounds depict bonds between two or more atoms of the same or different elements.
1) Once again, one must use an element’s electron configuration to determine its outer electrons. It is generally a good idea to draw the atom with the most outer electrons first.
2) When drawing this first atom of a molecular compound Lewis Dot Diagram, one must follow the same rules as one would when drawing a diagram for a single atom of the element.
3) The first atom should have one or more potential bonding sites (sides with less than two dots). 4) Draw the symbol of the any other atom next to the potential bonding sites. Use a small "x" in place of each dot when drawing this next atom. For this atom, draw the electrons in such a way that a bond is created at the potential bonding site. This means that on the side of the potential bonding site there is one dot and one "x". On a computer it is easier to use a "block" instead of an "x". Here are some examples of Lewis Dot Diagrams of molecular compounds: H2O NI3 O2 Mr. Curran's Lesson on Lewis Dot Diagrams Lewis Dot Diagram Practice Worksheet #1 Back to Fordham Prep Main Page Back to Mr. Curran's Main Page http://gibbs.lgc.peachnet.edu/chm101a/Lewis5.htm http://gibbs.lgc.peachnet.edu/chm101/Lewis.htm http://129.8.104.30:8080/~daidz/Chem3AF97/Lewis.html http://www.chem.vt.edu/chem-dept/deck/lewisdot.html Please forward all questions, comments and criticisms to Gregory L. Curran. |
