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### Drawing Lewis Structures

Posted: Sat Nov 02, 2019 1:57 pm
What is the best way to know how to draw lewis structures and where to put double bonds or single bonds? For example, how do you know where to put double bonds in ClO4-?

### Re: Drawing Lewis Structures

Posted: Sat Nov 02, 2019 2:00 pm
If there are multiple places you can place the double bond, that shows resonance. But you'll want to limit the formal charges on each atom.

### Re: Drawing Lewis Structures

Posted: Sat Nov 02, 2019 2:26 pm
I believe this is where finding the formal charges for each atom comes in and then placing the double bonds in a position that creates the lowest formal charge possible

### Re: Drawing Lewis Structures

Posted: Sat Nov 02, 2019 2:35 pm
Whenever you draw Lewis structures, you want to follow 3 steps:
1) Ensure that you have the correct number of valence electrons
2) Try to satisfy the octet rule when you can (be mindful of exceptions)
3) Try to get the lowest formal charges possible on each element

You start off everything with single bonds, and just begin to add double bonds when you're trying to fulfill the octet rule in a way that gives you the smallest formal charges.

### Re: Drawing Lewis Structures

Posted: Sat Nov 02, 2019 3:25 pm
Ally Huang- 1E wrote:What is the best way to know how to draw lewis structures and where to put double bonds or single bonds? For example, how do you know where to put double bonds in ClO4-?

With drawing Lewis Structures, the most important things is to draw the proper amount of electrons and the placement of the atoms (most electropositive in center). Knowing where the double and single bonds are located is based on the formal charges. First, calculate the formal charge or each atom. Then if the formal charge is negative, try to add a double bond to that atom and add lone pairs to make up the 2 e-. Do the opposite for a positive formal charge. Remember that you can have an expanded octet if n = 3 or if the element is after P.