Electron dot formulas of molecules

Here are the guidelines to placing electron dot diagrams of molecules

1. calculate the total number of valence electrons by adding all of the valence electrons for each atom in the molecule
2. divide the total valence electrons by 2 to find the number of electron pairs in the molecule
3. surround the central atom with 4 electron pair. use the remaining electron pairs to complete the octet around the other atoms
4. electron pairs that are shared by atoms are called bonding electrons. the other electrons complete octets and are called non bonding electrons, or lone pairs
5. if there are not enough electron pairs to provide each atom with an octet, move a non bonding electron pair between two atoms that already share an electron pair.

http://unothisblogiscool.blogspot.com/2011/05/electron-dot-diagrams.html

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