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### Double bond

Posted: Sat Oct 26, 2019 9:47 pm
How do you know when to double bond?

### Re: Double bond

Posted: Sat Oct 26, 2019 9:52 pm
One reason that a double bond may exist between two atoms is because it is the most stable, energetically. We sometimes add double bonds when drawing lewis structures because it decreases the number of lone pairs of electrons in the molecule.

### Re: Double bond

Posted: Sat Oct 26, 2019 9:53 pm
Two things to pay attention to are formal charge and octets. Most elements want to have a full shell of valence electrons, so try to make sure that they all have 8 electrons around them. Next is to pay attention to the formal charge. If by forming a double bond, the formal charge is closer to 0, then it would probably be a good idea to use a double bond.

### Re: Double bond

Posted: Sun Oct 27, 2019 10:20 pm
Add double bonds to a lewis structure when you still need to satisfy the octet rule after adding your valence electrons, or if it gives the molecule better formal charges.

### Re: Double bond

Posted: Sun Oct 27, 2019 10:25 pm
Sometimes, the octet rule will not be satisfied with simply using single bonds, and therefore double bonds would be necessary to satisfy this rule.

### Re: Double bond

Posted: Thu Oct 31, 2019 9:49 am
You typically use a double bond in your lewis structure to get the formal charge of an element to zero. For instance, oxygen often likes to double bond because the calculation FC=V-(L+s/2) would be 0=6-(4+4/2), stabilizing the molecule. Oxygen does not always double bond; this was just an example to help explain stabilization :)

### Re: Double bond

Posted: Thu Oct 31, 2019 10:56 am
Yes, like the answer above me said, you use double bonds to get the formal charge to 0. For example, if you have an oxygen atom bonded by a single atom with three lone pairs, you would not have a formal charge of 0 for oxygen. What you can do to fix that is change the single bond to a double bond and so now you have a double bond and 2 lone pairs. The formal charge would now be 0 for oxygen.

### Re: Double bond

Posted: Sat Nov 02, 2019 3:58 pm
You add double bonds to a lewis structure in order to satisfy the octet rule and make the molecule more stable. You would also add double bonds in order to decrease the formal charges of the molecule.

### Re: Double bond

Posted: Sat Nov 02, 2019 5:02 pm
Double bonds are used to satisfy the octet rule, which lowers the energy of the molecule, making it more stable.

### Re: Double bond

Posted: Sat Nov 02, 2019 5:05 pm
RobertXu_3K wrote:Two things to pay attention to are formal charge and octets. Most elements want to have a full shell of valence electrons, so try to make sure that they all have 8 electrons around them. Next is to pay attention to the formal charge. If by forming a double bond, the formal charge is closer to 0, then it would probably be a good idea to use a double bond.

Do you first try to satisfy the octet rule and then calculate formal charge or does it no matter which order you do them?

### Re: Double bond

Posted: Sat Nov 02, 2019 6:31 pm
Amina Durrani 3G wrote:
RobertXu_3K wrote:Two things to pay attention to are formal charge and octets. Most elements want to have a full shell of valence electrons, so try to make sure that they all have 8 electrons around them. Next is to pay attention to the formal charge. If by forming a double bond, the formal charge is closer to 0, then it would probably be a good idea to use a double bond.

Do you first try to satisfy the octet rule and then calculate formal charge or does it no matter which order you do them?

In the midterm review, the steps given were "electrons, octet, then formal charge". I think that by calculating the formal charge last, you can assess your Lewis structure and see if that is the most stable structure for the molecule.

### Re: Double bond

Posted: Sun Nov 03, 2019 9:56 pm
Most often double bonds are drawn in order to keep in line with the octet rule.

### Re: Double bond

Posted: Sun Nov 03, 2019 10:33 pm
Calculate formal charge of all the atoms of a molecule and see if the most stable configuration includes a double bond. They can help to stabilize the structure

### Re: Double bond

Posted: Sun Nov 03, 2019 11:27 pm
How would a double bond help stabilize a structure?

### Re: Double bond

Posted: Fri Nov 08, 2019 9:36 am
Ruby Richter 4G wrote:How would a double bond help stabilize a structure?

In most cases, it would help reduce the formal charge of the atom to 0. For example, oxygen with a single bond and 3 lone pairs has a formal charge of -1. But if you change its bond to a double bond with two lone pairs, it will have a formal charge of 0 and this will stabilize the structure.

### Re: Double bond

Posted: Sun Nov 17, 2019 5:25 pm
A double bond stabilizes the structure by bringing the formal charge closer to or equal to 0. A Lewis structure is most stable when the central atom has a formal charge of 0 and in some cases, a double bond is needed to achieve this.