sigma vs pi bonds

(Polar molecules, Non-polar molecules, etc.)

Moderators: Chem_Mod, Chem_Admin

Queena Chu 3E
Posts: 55
Joined: Wed Sep 30, 2020 10:09 pm

sigma vs pi bonds

Postby Queena Chu 3E » Sat Nov 28, 2020 11:23 pm

How do we determine sigma vs pi bonds? Are sigma or pi bonds stronger?

Chloe Little 3K
Posts: 70
Joined: Wed Sep 30, 2020 10:02 pm
Been upvoted: 1 time

Re: sigma vs pi bonds

Postby Chloe Little 3K » Sat Nov 28, 2020 11:44 pm

All single bonds are sigma bonds. A double bond has one sigma bond and one pi bond. And a triple bond has one sigma bond and two pi bonds.

Eliana Carney 3E
Posts: 61
Joined: Wed Sep 30, 2020 9:31 pm

Re: sigma vs pi bonds

Postby Eliana Carney 3E » Sun Nov 29, 2020 12:38 am

Hey Queena!
A sigma bond occurs when two orbitals interact end-to-end and form a bond. A pi bond occurs when two orbitals overlap side-by-side and form a bond. Pi bonds can only form if an atom's electron configuration includes a d-orbital because without a d-orbital there is only one orbital, the s-orbital, and there are not two orbitals to overlap. When looking at a Lewis structure, you can count the amount of sigma bonds and pi bonds because a single bond has one sigma bond, a double bond has one sigma bond and one pi bond, and a triple bond has one sigma bond and two pi bonds.
As for which bond is stronger, sigma bonds are stronger than pi bonds because of the amount of overlap. There is more overlap in one sigma bond because the orbitals are completely overlapping along the internuclear axis while in a pi bond the orbitals are only partially overlapping above and below the internuclear axis.
Hope this clears some things up!

Ximeng Guo 2K
Posts: 69
Joined: Wed Sep 30, 2020 9:54 pm

Re: sigma vs pi bonds

Postby Ximeng Guo 2K » Sun Nov 29, 2020 8:06 am

To add on, a double bond is stronger than a single bond as bond length is shorter. Not sure whether we can determine a sigma bond is stronger than a single pi bond.

Grace_Remphrey_2J
Posts: 60
Joined: Wed Sep 30, 2020 9:54 pm

Re: sigma vs pi bonds

Postby Grace_Remphrey_2J » Sun Nov 29, 2020 2:33 pm

Sigma and pi bonds are chemical covalent bonds. Sigma and pi bonds are formed by the overlap of atomic orbitals. Sigma bonds are formed by end-to-end overlapping and Pi bonds are when the lobe of one atomic orbital overlaps another. Generally, sigma bonds are stronger than pi bonds because sigma bonds allow for electron density to be concentrated to a much larger degree between the two nuclei.

apurva-3E
Posts: 92
Joined: Wed Sep 30, 2020 9:59 pm

Re: sigma vs pi bonds

Postby apurva-3E » Sun Nov 29, 2020 2:57 pm

Single Bond = Sigma
Double Bond = Sigma and Pi Bond
Triple Bond = Sigma and 2 Pi Bonds

Determining bond strength between sigma and pi bonds won't be tested. However, single bonds are longer and weaker than double bonds.

Simran Bains 2C
Posts: 60
Joined: Wed Sep 30, 2020 9:36 pm

Re: sigma vs pi bonds

Postby Simran Bains 2C » Sun Nov 29, 2020 2:58 pm

A single bond is a sigma bond and then any bond after that is a pi bond. For example, with a double bond, there is one sigma bond and one pi bond. A triple bond has one sigma bond and two pi bonds.

rhettfarmer-3H
Posts: 69
Joined: Wed Sep 30, 2020 9:59 pm

Re: sigma vs pi bonds

Postby rhettfarmer-3H » Sun Nov 29, 2020 4:46 pm

Sigma is a correlation of one bond. It is also one bond in the double bond and so in always one sigma bond. Furthermore, pi bonds are the spots onwards on the double bonds and triple. the big difference is that sigma bonds can rotate by the feature of them being tied in less rigid way in comparison to the pi bond which has two regions that tie together which causes no movement.

Jared Limqueco 3E
Posts: 60
Joined: Wed Sep 30, 2020 9:37 pm

Re: sigma vs pi bonds

Postby Jared Limqueco 3E » Sun Nov 29, 2020 4:50 pm

A single bond is one sigma, double is sigma + pi, and triple is sigma + 2 pi. If you recall, the more bonds the shorter the distance btwn two atoms, so the stronger the bond.

Stephen Min 1I
Posts: 60
Joined: Wed Sep 30, 2020 10:01 pm

Re: sigma vs pi bonds

Postby Stephen Min 1I » Sun Nov 29, 2020 5:20 pm

Because pi bonds consist of 2 or more bonds, they are considered stronger than the single (sigma) bonds. The strength of pi bonds also means that atoms connected by the bond cannot rotate, whereas sigma bonds can allow for rotation.

Kat Stahl 2K
Posts: 62
Joined: Wed Sep 30, 2020 10:03 pm

Re: sigma vs pi bonds

Postby Kat Stahl 2K » Sun Nov 29, 2020 5:30 pm

When I looked it up (because I was also confused) I found a website that stated the following: Sigma bonds are formed by head-on the overlap of atomic orbitals. Whereas pi bonds are formed in addition to sigma bonds by sideways overlapping of atomic orbitals. Since the information of a sigma bond, the orbitals are along internuclear axis this results in more effective orbital overlap as compared to when pi bonds are formed as they are perpendicular to the internuclear axis. This significant difference in orbital overlap results in sigma bond being stronger than the pi bond.
I found this on: https://www.toppr.com/ask/question/expl ... pipi-bond/
Hope this helps!

YUNALEE
Posts: 53
Joined: Wed Sep 30, 2020 9:42 pm

Re: sigma vs pi bonds

Postby YUNALEE » Sun Nov 29, 2020 5:49 pm

I also saw in the textbook that side - side bonds are sigma and others are pi bonds
also, s in sigma signifies the s orbital and same w p in pi with the p orbital

Ashley Kim 3H
Posts: 61
Joined: Wed Sep 30, 2020 9:34 pm
Been upvoted: 2 times

Re: sigma vs pi bonds

Postby Ashley Kim 3H » Sun Nov 29, 2020 6:02 pm

We can determine the number of sigma and pi bonds depends on what type of bond it is (single, double, or triple). As we know, triple bonds are stronger than double, which are stronger than single.

Arnav Saud 2C
Posts: 84
Joined: Wed Sep 30, 2020 9:51 pm

Re: sigma vs pi bonds

Postby Arnav Saud 2C » Sun Nov 29, 2020 6:07 pm

Single bonds only have sigma bonds while double bonds have one sigma and one pi bond. A triple bond has 1 sigma bond and 2 pi bonds.
Sigma bonds allow for flexibility of a molecule, which, as seen Dr. Lavelle's lecture with his marker demonstration, allows for the structure to bend without breaking.
Pi bonds make the structure more rigid and when flexed, the bonds are more likely to break.

Savannah Torella 1L
Posts: 52
Joined: Wed Sep 30, 2020 9:40 pm

Re: sigma vs pi bonds

Postby Savannah Torella 1L » Sun Nov 29, 2020 6:30 pm

When looking at atomic orbital models, a sigma bond is present when the ends of the orbitals interact with each other. A pi bond is present when the orbitals overlap side to side, crossing paths twice instead of once. When looking at Lewis structures and VSEPR models, a sigma bond is present when there is a single bond. When there is a double bond, there is one sigma bond and one pi bond. When there is a triple bond, there is one sigma bond and two pi bonds. I would assume that pi bonds are stronger since they are included in double bonds, which are stronger than the single bonds containing a sigma bond.

Madeline Marron 1I
Posts: 50
Joined: Wed Sep 30, 2020 10:01 pm

Re: sigma vs pi bonds

Postby Madeline Marron 1I » Sun Nov 29, 2020 6:34 pm

single bond is sigma, double bond is one sigma and one pi, a triple is one sigma and two pi bonds

Justin Zhang_1A
Posts: 60
Joined: Wed Sep 30, 2020 9:48 pm

Re: sigma vs pi bonds

Postby Justin Zhang_1A » Sun Nov 29, 2020 6:34 pm

You can determine sigma and pi bonds depending on whether it is a single, double, or a triple bond. All single bonds only have sigma bonds, whereas a double bond has one sigma bond and one pi bond. Likewise, a triple bond has one sigma bond and two pi bonds. A single sigma bond is flexible, which makes it easier to break. However, when you begin to add pi bonds in a double and triple bond, the bond strength increases, and it becomes harder to break.

Brandon Pham 1B
Posts: 51
Joined: Wed Sep 30, 2020 9:59 pm
Been upvoted: 1 time

Re: sigma vs pi bonds

Postby Brandon Pham 1B » Sun Nov 29, 2020 6:41 pm

All bonds contain 1 sigma bond each.
Double bonds contain 1 sigma and 1 pi
Triple bonds contain 1 sigma and 2 pi

FionaHunter21
Posts: 60
Joined: Wed Sep 30, 2020 9:37 pm

Re: sigma vs pi bonds

Postby FionaHunter21 » Sun Nov 29, 2020 6:58 pm

Do pi bonds only occur in double and triple bonds? Or can be somewhere else where there are orbitals side by side?

Ruth Rosales 3D
Posts: 58
Joined: Wed Sep 30, 2020 9:44 pm
Been upvoted: 1 time

Re: sigma vs pi bonds

Postby Ruth Rosales 3D » Sun Nov 29, 2020 7:12 pm

This is how I am memorizing it:

- single bond = 1 sigma bond
- double bond = 1 sigma and pi bond
- triple bond = 1 sigma and 2 pi bonds

so each bond has one sigma bond and the pi bonds go increasing from double to triple bond by 1.

Hope this helps

Chudi Onyedika 3A
Posts: 62
Joined: Wed Sep 30, 2020 9:37 pm

Re: sigma vs pi bonds

Postby Chudi Onyedika 3A » Sun Nov 29, 2020 7:46 pm

A sigma bond is stronger than a pi bond

Meghan Krushena 2E
Posts: 60
Joined: Wed Sep 30, 2020 10:10 pm

Re: sigma vs pi bonds

Postby Meghan Krushena 2E » Sun Nov 29, 2020 7:49 pm

a sigma bond is a single bond that allows free rotation. A pi bond does not allow rotation along the internuclear axis. A double bond is consistent of one sigma bond and one pi bond, the order does not matter. A triple bond is one sigma bond and 2 pi bonds

Hailey Kang 2K
Posts: 66
Joined: Wed Sep 30, 2020 10:03 pm

Re: sigma vs pi bonds

Postby Hailey Kang 2K » Sun Nov 29, 2020 7:59 pm

Hi! Single bonds are always sigma bonds. Double bonds have 1 sigma and 1 pi, and triple bonds have 1 sigma and 2 pi

Eve Gross-Sable 1B
Posts: 61
Joined: Wed Sep 30, 2020 10:02 pm
Been upvoted: 1 time

Re: sigma vs pi bonds

Postby Eve Gross-Sable 1B » Sun Nov 29, 2020 8:09 pm

How do you determine if the overlap is end to end vs side to side? They look basically the same in the diagrams. Thanks!

Chinmayi Mutyala 3H
Posts: 63
Joined: Wed Sep 30, 2020 9:50 pm

Re: sigma vs pi bonds

Postby Chinmayi Mutyala 3H » Sun Nov 29, 2020 8:11 pm

Single bonds are sigma bonds and double bonds have one sigma and one pi bond. The difference is that in sigma bonds, the ends of the orbitals overlap and in pi bonds, parallel orbitals overlap side to side.

Kelly Tran 1J
Posts: 103
Joined: Wed Sep 30, 2020 9:50 pm
Been upvoted: 1 time

Re: sigma vs pi bonds

Postby Kelly Tran 1J » Sun Nov 29, 2020 8:42 pm

Hi! A sigma bond is a bond that is formed when two orbitals, each with 1 electron, interact end-to-end. A pi bond, on the other hand, is a bond that is formed when two orbitals, each with 1 electron, overlap side-by-side. All single bonds are sigma bonds. A double bond has one sigma bond and one pi bond. A triple bond has one sigma bond and two pi bonds. Hope this helps!

Jerry_T
Posts: 64
Joined: Wed Sep 30, 2020 9:46 pm

Re: sigma vs pi bonds

Postby Jerry_T » Sun Nov 29, 2020 9:03 pm

All single bonds are sigma bonds. Consequently, double bonds have one sigma and one pi bonds and triple bonds have one sigma and two pi bonds. (i.e. The bonds in addition to one sigma bond are all pi bonds). Pi bonds are stronger than sigma bonds. You can conceptually verify this because triple bonds are stronger than single bonds which have no pi bonds.

Abraham De Luna
Posts: 57
Joined: Sat Sep 14, 2019 12:16 am

Re: sigma vs pi bonds

Postby Abraham De Luna » Sun Nov 29, 2020 9:33 pm

Typically, all single bonds have one sigma bond and all double bonds have one sigma bond and one pi bond. Also, a triple bond would have a one sigma bond and two pi bonds. So when you are counting the amount of sigma bonds in a molecule make sure to consider the sigma bonds present in double and triple bonds.

Diana Aguilar 3H
Posts: 60
Joined: Wed Sep 30, 2020 9:50 pm

Re: sigma vs pi bonds

Postby Diana Aguilar 3H » Sun Nov 29, 2020 9:38 pm

All single bonds contain a sigma bond, double bonds contain a sigma bond and a pi bond, and lastly a triple bond has one sigma bond and two pi bonds.

Mackenzie Van Val 3E
Posts: 69
Joined: Wed Sep 30, 2020 9:36 pm

Re: sigma vs pi bonds

Postby Mackenzie Van Val 3E » Sun Nov 29, 2020 9:45 pm

Single bonds are sigma bonds. Double bonds contain a pi and a sigma bond, and a triple bond has one sigma and two pi bonds. Therefore, all three contain sigma bonds. Something that helps me remember the number of pi bonds in a bond type is that for double and triple bonds, the number of pi bonds is the number of the bond minus one. For example, a double bond = 2. 2-1=1. So, there is one pi bond in a double bond.

Irene Nguyen 3H
Posts: 49
Joined: Wed Sep 30, 2020 9:44 pm

Re: sigma vs pi bonds

Postby Irene Nguyen 3H » Sun Nov 29, 2020 9:55 pm

Single bond = 1 Sigma bond
Double bond = 1 Sigma bond and 1 Pi bond
Triple bond = 1 Sigma bond and 2 Pi bonds

I'm not completely sure on bond strength, but I believe Pi bonds are stronger as triple bonds are stronger than double bonds. Checking the relation between the three bonds, if a triple bond is stronger with one more Pi bond than a double bond, then it seems to imply that a Pi bond is stronger than a Sigma bond.

Zach Richardson 2f
Posts: 55
Joined: Wed Sep 30, 2020 9:32 pm

Re: sigma vs pi bonds

Postby Zach Richardson 2f » Sun Nov 29, 2020 9:59 pm

I know that a souble bond has to be a pi-bond, but I am slightly confused as to why. In lecture Dr. Lavelle explained it as if it should make sense that because a pi-bond forms side-by-side that it would be the double bond but I didn't understand :(. Why is this true?

kristinalaudis3e
Posts: 61
Joined: Wed Sep 30, 2020 10:11 pm
Been upvoted: 1 time

Re: sigma vs pi bonds

Postby kristinalaudis3e » Sun Dec 06, 2020 11:26 pm

Sigma bonds are in all bonds while pi bonds are only in double and triple bonds. In a single bond there is only one sigma bond. In a double bond, there is one sigma and one pi bond and in a triple bond there is one sigma and 2 pi bonds.

Danielle DIS2L
Posts: 61
Joined: Wed Sep 30, 2020 9:38 pm

Re: sigma vs pi bonds

Postby Danielle DIS2L » Sun Dec 06, 2020 11:39 pm

single bonds=sigma bonds
double bonds= one sigma bond and one pi bond
triple bonds=one sigma and two pi bonds


Return to “Determining Molecular Shape (VSEPR)”

Who is online

Users browsing this forum: No registered users and 2 guests