Single or Double Bonds

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Hailey Kim 4G
Posts: 110
Joined: Sat Jul 20, 2019 12:16 am

Single or Double Bonds

Postby Hailey Kim 4G » Fri Oct 25, 2019 4:07 pm

When drawing Lewis Structures, how do you know when you're supposed to use a single or double bond?

Jessica Li 4F
Posts: 115
Joined: Fri Aug 09, 2019 12:16 am

Re: Single or Double Bonds

Postby Jessica Li 4F » Fri Oct 25, 2019 4:14 pm

For elements who cannot have expanded octets, you want to draw bonds in a way so all elements (except H and He) have octets. For instance, CO2 would need double bonds, while CF4 only needs single bonds.
For elements who can have expanded octets, you want to calculate the formal charges of all the atoms and figure out which structure would be the most stable (has the least formal charge).

Nikita Patra 3J
Posts: 50
Joined: Sat Jul 20, 2019 12:16 am

Re: Single or Double Bonds

Postby Nikita Patra 3J » Fri Oct 25, 2019 4:16 pm

You count the number of valence electrons and follow the octet rule. Another way to do it would be to calculate the formal charge on each atom.

605379296
Posts: 58
Joined: Sat Aug 17, 2019 12:16 am

Re: Single or Double Bonds

Postby 605379296 » Fri Oct 25, 2019 4:20 pm

You use a double bond according to the octet rule where you want the middle element to have a full valence shell of eight electrons.

Vincent Leong 2B
Posts: 207
Joined: Fri Aug 09, 2019 12:15 am

Re: Single or Double Bonds

Postby Vincent Leong 2B » Fri Oct 25, 2019 4:22 pm

It depends largely on the amount of valence electrons a certain atom has and the fact that the atom is trying to fill the octet rule.

As we went over in class today, formal charge is also a large factor in determining whether a double bond is preferred over a single bond.


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