### AXE formula

Posted:

**Sun Jun 03, 2018 10:51 pm**is it possible to determine the shape of a molecule if you're only given the AXE formula, if so how do you do it?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=43&t=32276

Page **1** of **1**

Posted: **Sun Jun 03, 2018 10:51 pm**

is it possible to determine the shape of a molecule if you're only given the AXE formula, if so how do you do it?

Posted: **Sun Jun 03, 2018 10:54 pm**

It is possible. The AXE formula tells you how many regions of electron density there are, which ones are specifically bonding pairs, and which ones are lone pairs. This is all that is needed to determine molecular shape.

Posted: **Sun Jun 03, 2018 10:57 pm**

The chart below will be helpful

Posted: **Sun Jun 03, 2018 10:58 pm**

From what i understand it is necessary to know the shape that corresponds to the formula. This means memorizing which formulas are associated to which shape.

Posted: **Sun Jun 03, 2018 11:04 pm**

Yes. A represents the center atom, X represents atoms bonded to the center atom, and E represents lone electron pairs. X and E together represent regions of electron density.

Each AXE formula corresponds to a different molecular structure shown in the chart posted by Jack.

Each AXE formula corresponds to a different molecular structure shown in the chart posted by Jack.

Posted: **Sun Jun 03, 2018 11:05 pm**

I believe if they give you the molecular formula and the AXE formula you could determine the shape. Say if you were given H2O: AX2E2... then you know there are 2 bonding atoms and 2 lone pairs. Then once you draw the molecule out you could figure out its shape.

Posted: **Sun Nov 18, 2018 11:00 pm**

Enzo_1I wrote:From what i understand it is necessary to know the shape that corresponds to the formula. This means memorizing which formulas are associated to which shape.

do you happen to know if theres anyway to know the corresponding shape aside form the AXE formula? or must we memorize those too?

Posted: **Mon Nov 19, 2018 1:16 pm**

There really isn't another way, the best thing to do is just memorize them because the AXE formula tells you what shape the molecule is.

Posted: **Fri Nov 23, 2018 8:36 pm**

The only way for you to know the shapes is to simply memorize them using the table above or one that you can search up online. By knowing AXE, that should in turn help you figure out the different geometric shapes of each molecule.

Posted: **Wed Nov 28, 2018 9:09 pm**

Yes. With the AXE formula you can deduce what shape and bond angle the molecule will have based on charts and tables.

Posted: **Sat Dec 01, 2018 3:16 pm**

Also be aware that AXE is a specific VSEPR Group that will help you determine MG or molecular geometry.

Posted: **Sat Dec 01, 2018 5:19 pm**

yes you can determine the molecular shape of the molecule, knowing the AXE formula because the number of electron densities are known. By counting the number of lone pairs and the number of atoms around the central atom you can know the shape and bond angles.

Posted: **Sat Dec 01, 2018 5:40 pm**

It's possible but be aware of that there are molecules with different shapes but same AXE Formula. This is because they have the same number of electron densities. For instance, tetrahedral and trigonal pyramidal are both AXE4 because they both have 4 regions of electron densities.

Posted: **Sat Dec 01, 2018 8:10 pm**

To learn these I just made a chart, or you can write down the one posted above as it can be super helpful, and then put it all into flashcards on quilt. I studied that until i had it memorized, then, doing a bunch of problems switches the memorization from route to actual understanding.

Posted: **Sun Dec 02, 2018 8:00 pm**

Yes with the AXE formula you can determine the shape of the molecule

Posted: **Mon Dec 03, 2018 6:00 pm**

Yes, the AXE formula can help you draw the shape of the structure, but it will not tell you the elements involved.

Posted: **Mon Dec 03, 2018 8:27 pm**

How do we figure out the AXE formula? I am still having trouble with this.

Posted: **Thu Dec 06, 2018 6:03 pm**

danielruiz1G wrote:is it possible to determine the shape of a molecule if you're only given the AXE formula, if so how do you do it?

Yes because the AXE formula tells you the regions of electron density which is all you need to determine the shape.

Posted: **Thu Dec 06, 2018 6:05 pm**

Arlene Linares 3A wrote:How do we figure out the AXE formula? I am still having trouble with this.

A is the central atom. X is the number of atoms bonded to the central atom. E is the number of lone pairs on the central atom.

Posted: **Sat Jul 20, 2019 6:25 pm**

Yes, you can determine shape with the AXE formula. You should try to memorize them because it'll save time and guarantee correctness on exams, but you can also think about it in terms of regions of electron density, where X represents bonding pairs on the central atom and E represents lone pairs on the central atom.

Posted: **Sun Nov 17, 2019 1:10 am**

By knowing the central atom as well as how many lone pairs and bonded atoms there are, it can be deduced which shape the molecule is.

Posted: **Sun Nov 17, 2019 1:46 pm**

Yes it is! Any molecule with the same AXE formula will have the same molecular shape/

Posted: **Sun Nov 17, 2019 4:12 pm**

Yes, you should be able to determine the shape of a molecule based on the AXE formula.

Posted: **Sun Nov 17, 2019 4:15 pm**

Is the AXE formula another name for the VSEPR formula? Are the two terms interchangeable?

Posted: **Sun Nov 17, 2019 4:17 pm**

This notation lets us know the number of bonding pairs and lone pairs which makes it easier to draw structures.

Posted: **Sun Nov 17, 2019 4:22 pm**

Yes you can, and they will. usually be the same. Looking at the AXE formula, X is number of bonded pairs to central atoms and E is number of lone pairs. With this you can understand the number of electron densities but also the number of bonded atoms. So you can use both to figure out the shape and the angles usually

Posted: **Sat Nov 23, 2019 4:09 pm**

danielruiz1G wrote:is it possible to determine the shape of a molecule if you're only given the AXE formula, if so how do you do it?

The only real way to do it, is to memorize the chart. This chart is especially helpful because it includes hybridization and shape and polarity.

Posted: **Sat Nov 23, 2019 11:49 pm**

danielruiz1G wrote:is it possible to determine the shape of a molecule if you're only given the AXE formula, if so how do you do it?

The formula tells you how many lone pairs as well as how many attached atoms there are to the central atom.

The subscript after X is how many atoms attached to the central atom. In AX2E2 for example, there are two attached atoms.

The subscript after E refers the the number of lone pairs. For AX2E2 ther are two lone pairs.

So, putting all the information together, there are two attached atoms and two lone pairs, so we have the electron shape as tetrahedral, and the molecular shape as bent. Water has this formula. I think that as long as you know the VSEPR shapes you can deduce the formula.

Posted: **Sun Nov 24, 2019 1:28 am**

Yes, it's definitely possible! You just have to be able to know which formula corresponds with which shape.

Posted: **Sun Nov 24, 2019 2:44 am**

It is possible to determine the molecular shape from AXE formula. The formula corresponds to the number of electron densities, including the lone pairs and bonds, which is then used to determine shape of the molecule.

Posted: **Sun Nov 24, 2019 3:21 pm**

Yes, you can determine the molecular shape from the formula. The subscript off of Xn tells you how many things are bonded to the central atom, and the subscript off of Em tells you how many lone pairs there are on the central atom. With this information, we can figure out the molecular shape. I suggest making flashcards from the charts posted above to make this easier! It's definitely something we need to memorize :)

Posted: **Sun Dec 01, 2019 9:25 pm**

Yes, the AXE formula is part of VSEPR Theory, which is used to determine a molecule's shape. Just remember that you can't use hybridization to determine a molecule's shape!

Posted: **Sun Dec 01, 2019 9:27 pm**

The best way is to know the chart and which shape corresponds with which AXE formula.