Covalent Bonding
Also called Molecular Bonding - uses non-metals only.
Lewis Dot Structures are used to show the how and where the elements are bonded together, along with any unbonded valence electrons.
This video can help get you started with Lewis Dot Structures. The powerpoint slides are posted below.
Overview of the RULES FOR DRAWING LEWIS DOT STRUCTURES:
Rule 1 - Count the number of valence electrons each atom HAS.
Rule 2 - Count the number of valence electrons each atom WANTS.
- Hydrogen only wants 2
- Boron only wants 6
- Pretty much everything else will want 8
Rule 3 - Subtract the above (Rule 2 minus Rule 1) to get the number of electrons that will be used in BONDING.
Rule 4 - Divide THAT in half (Rule 3 divided by two) to get the number of actual BONDS (a line).
Rule 5 - Start drawing:
- If you have Carbon - put that in the middle
- Never put Hydrogen in the middle (it will usually be on the edges of the structure)
- No Carbon? Use the element that is the least electronegative (use the Paulings table, or make an educated guess based on Periodic Trends!) in the middle. But not Hydrogen!
- Balance the remaining elements as evenly as you can around the central one
- Draw single bonds between all the elements
- If you still need to use more bonds (check Rule 4), then add double bonds, or triple bonds where needed.
* Carbon family - 4 bonds
* Nitrogen family - 3 bonds
* Boron (element) - 3 bonds!
* Oxygen family - 2 bonds
* Fluorine family (aka The Halogens) - 1 bond
* Hydrogen - 1 bond
*** If you stop here, it would be a "Structural Formula" for the molecule.
Rule 6 - Subtract electrons used from electrons that we have (Rule 1 minus Rule 3) to get the number of electrons that will be left over. That will be the number of valence electrons that are NOT bonded. Draw those as Lewis dots where needed. Remember!!! Each bond (line) counts as two electrons!!!
* I hope this helps!!!
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