Double Bonds

[Vy Le 1G]

I need help with knowing when to use double bonds and when not to. I know we want the most stable version but how do I know when to use a double bond versus variations of a single bond and so forth? Thank you in advance!

[205783236]

hi! I believe that you can use double bonds when you are trying to create that octet or when you realize that the formal charges when you use single bonds is not 0 and therefore unstable.

[Vivek Chotai 2C]

Use a double bond (or maybe even a triple if you need) if you don't have enough valence electrons in your diagram. This way, instead of using lone pairs to fill 1 atom's octet, you can use the same number of electrons to form a bond (sharing electrons) and fill both atoms' octets.

[MaiVyDang2I]

Hey! Usually I would start out by counting the number of valence electrons, then I would sketch the skeleton structure of the Lewis structure (the central atom and other atoms' positions relative to the central atom). Then I'd connect all of them using single bonds and count the number of valence electrons that I have. If the amount is not equal to what I counted initially, I'd add double bond(s) and triple bond(s) as needed to reach the amount I first counted. Hope this helps!

[Sarah Lesmeister 2F]

Hi! You can use double bonds when you need to achieve the octet rule, but don't have enough electrons or have too many because the number calculated isn't the same as what you have drawn in your diagram. Like in the lecture today, we had too many electrons in NO3 so we created a double bond.

[ashna kumar 3k]

A lot of times, we also use double bonds in resonance structures and to get formal charges closer to 0 for a more stable Lewis Structure. If you remember, the first lecture we drew the sulfate ion, we drew it with all single bonds. However, in today's lecture when we learned resonance and formal charges, we realized that the formal charge is lower when we have two double bonds on sulfur and allow it to have an expanded octet. Thus double (and triple) bonds are used when there aren't enough valence electrons but also when there is a need to make the formal charge lower and the whole molecule more stable.

[Ainsley McCabe 2D]

The goal in drawing lewis structures is to find a structure that is the most stable. We can do this by looking at the formal charges for each atom in a molecule and in doing this we also figure out when to use double bonds. Take the example of the sulfate ion in class, we thought we had a stable structure, but in looking at the formal charges realized we could make the structure even more stable by adding double bonds. So it is best to look at the formal charges when deciding whether or not to use a double bond.

[Hannah Carsey 1B]

Double and triple covalent bonds occur when four (two sets of two electrons: double bond) or six electrons (three sets of two electrons: triple bond) are shared between two atoms, and they are indicated in Lewis structures by drawing two or three lines connecting one atom to another. Each atom in a Lewis structure has an octet (eight) of electrons, so determine how to configure each atom to have eight electrons by using a combination of unpaired electrons, single bonds (one pair of electrons: single bond), double bonds, or triple bonds. Most structures—especially those containing second row elements—obey the octet rule, in which every atom (except H) is surrounded by eight electrons.

[605778346]

Hi, we can use double bonds when we are trying to achieve an octet within the atom.

[Vivian Kim 3F]

Hey, I just wanted to add that in addition to paying attention to the octet rule and formal charge, you should also keep in mind that there are some exceptions to the octet rule. For instance, elements past (I believe) 2nd period or row can have more than 8 electrons.

[405716590]

If the double bond makes the formal charge of each atom closer to 0 then it should be used.

[Clarence Clavite 2K]

So usually you would only use a double bond if there are enough electrons to for it to occur and if there is an unsatisfied atom. So an atom trying to reach an octet. Hope this helps!

[Alekhya_Pantula_2E]

Hi! Double bonds are usually used in cases when we want to get a formal charge of 0 or so we can satisfy the octet rule.

[Trisha Nagin]

When we want to achieve octet or satisfy the formal charge of 0 we would usually use a double bond.

[Aashna Bhandari 1L]

Double bonds are usually used when you are trying to complete an octet for two of the elements involved in the molecule or if the formal charge of the element in the molecule is less that way.

[Rio Gagnon 1G]

Typically, we use double (or triple) bonds when trying to fit the octet rule or when the molecule has either too many or not enough valence electrons. You can determine if it is better to use a double bond or not by looking at the formal charge of each element.

[Ivy Vo Dis 1C]

There are two main instances in which double bonds would be used in a Lewis dot structure. First, if you do not have enough electrons to complete the octet rule for each element in the structure, you can use double bonds to fulfill the 8 valence electron requirement. Rather than using 8 individual electrons to fill 2 orbitals per 2 different atoms, you could place a double bond to use 4 electrons to fill 2 orbitals for 2 different atoms. Second, you should use a double bond if it brings the formal charges of each element closer to 0.