​Lewis dot diagram is a useful tool for us to study chemistry. Some times it's difficult for student do draw since they feel confused. So first of all, let's see what is a Lewis dot diagram!


"Lewis structures, also called Lewis dot diagrams, electron-dot diagrams or electron-dot structures, are diagrams that show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule...The Lewis structure was named after Gilbert N. Lewis, who introduced it in his 191 article The Atom and the Molecule..."--http://en.wikipedia.org/wiki/Lewis_structure

Lewis_dot_diagram.gif(from: http://www.shfle.com/sat/test/2008-12-17/21328_4.html)

*Usually, in a Lewis dot diagram short dash between two elements means a bond. If there's only two single dots, it means a lone pair exits.

*Except hydrogen and helium, other elements have 8 electrons in the outer shell.













NOW, LET'S BEGIN TO PLAY!!
1). Use the table below to count how many valence electrons are being hold in the covalent compound.
Number of Valence Electrons
1
2
3
4
5
6
7
8
Example
Hydrogen
Group I
(Alkali metals)
Helium
Group II
(alkali earth metals)
Group III
Group IV
Group V
Group VI
Group VII
(Halogens)
Group VIII except Helium
(Noble Gases)
Lewis Structure
(electron dot diagram)

.gif
.gif
.gif
.gif
.gif
.gif
.gif
.gif
.gif
.gif
2). Look at the givin structure and time the # of bond by 2 to get the electrons that have been used.

3). Use the total number of valence electrons minus the result you get on the second step to figure out how many electrons can still be used.




EX: NF*N has1 valence electrons of 5 and F has the valence electrons of 7. For total, therea are 26 of them.
0.gif
*Accroding to the give structure, H-F has ONE bond which means there are 2 electrons that have been used.


1.gif
http://www.green-planet-solar-energy.com/lewis-dot-structure.html











4). Put those electrons around the atoms and try to let every one of them have the full outershell with 8 electrons.
*Bonds(represents 2 electrons) are counted in both atoms it connects.
*When there is lack of electrons you can create bonds to make the elements full.
lewis-dot-diagram.gif
5). When every element (except H and He) get their valence electrons full, you're succeed!
EX​​: In oxygen gas, each oxygen atom holds 6 valence electrons. When you draw the Lewis Dot Daifram as they share 1 bond, each oxygen atom has 7 valence electrons. Now, we still need one electron on each side. So what can we do? Obvious to see, in the diagram we have 2 unpaired electrons on each side. The interesting thing is, when we join these two single electrons together, each oxygen atoms gets one extra electron since they share electron with each other. Redraw the structure with two bonds between the atoms and 8 electrons left around, what do you see? Two oxygen both reach the balance state.

​ ​Congratulations!!--now you have hold "drawing the Lewis Dots Diagram of covalent compound" in hand!!

In addition, if you have further questions please ask me, or have a look on these websites: http://www.ausetute.com.au/lewisstr.html, http://www.ehow.com/how_4505765_draw-electron-dot-diagrams.html ,http://faculty.uscupstate.edu/cbender/Web%20page%20folder%20enmass/chm111/Chm%20111%20worksheets/LewisVSEPRanswers.htmland http://www.ehow.com/how_4711889_draw-lewis-dot-diagrams.html.


CREATED BY MELODY LI BLOCK A