Tips on drawing Lewis structures

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Bronson Mathos 1H
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Tips on drawing Lewis structures

Postby Bronson Mathos 1H » Sun Nov 29, 2020 3:38 am

Hello, after seeing my midterm score I believe I may not be very keen on drawing Lewis structures and I was wondering if anyone could give me some tips or a basic outline that will help me draw Lewis structures in the future. Thanks in advance!

Selena Quispe 2I
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Re: Tips on drawing Lewis structures

Postby Selena Quispe 2I » Sun Nov 29, 2020 3:57 am

Hi! So I like to calculate how many valence electrons I should have and then count the electrons again to make sure that I have drawn the lewis structure correctly. Also calculate the formal charges and remember you want the most stable/less charged structure. However, if you do have a charge like let's say a negative charge remember that the element that is the most electronegative will want to have that charge like for example the halogen group. Also memorize that carbon will form 4 bonds, oxygen prefers a double bond, nitrogen will want to form a triple bond, and halogens like to form one bond. I hope this helps!!

Veeda Khan 2E
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Re: Tips on drawing Lewis structures

Postby Veeda Khan 2E » Sun Nov 29, 2020 5:22 am

The most important part is to make sure you have the appropriate number of valence electrons in your structure. Once you get that down, find the formal charge to make sure you have the most stable structure.

905409193
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Re: Tips on drawing Lewis structures

Postby 905409193 » Sun Nov 29, 2020 7:14 am

The best advice I can give is counting how many valence electrons there should be and to make sure to find the number of electrons needed to fill their octets when applicable.

Grace_Remphrey_2J
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Re: Tips on drawing Lewis structures

Postby Grace_Remphrey_2J » Sun Nov 29, 2020 2:40 pm

Hi! Here are the general steps I follow when drawing lewis structures.
First, determine the total number of valence electrons in a molecule. Second, draw a skeleton for the molecule which connects all atoms using only signal bonds. Third, arrange the remaining electrons to fill as many octets as possible. If the octets of atoms are not filled, make lone pairs of electrons into bonding pair of electrons that share with the atom that was initial electron deficient. Lastly, check that you have the lowest formal charges while still respecting the octet rule. Hope this helps!

Simran Bains 2C
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Re: Tips on drawing Lewis structures

Postby Simran Bains 2C » Sun Nov 29, 2020 3:02 pm

I would say to start with the valence electrons and then put the least electronegative atom in the center. Then orient the other atoms around and base the bonds on the charge of each atom.

LeanneBagood_2F
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Re: Tips on drawing Lewis structures

Postby LeanneBagood_2F » Sun Nov 29, 2020 8:18 pm

To add on to this, are there any Lewis structures that you all think we should all be pretty solid with? Like not necessarily know them by heart but be able to do them with ease if that makes sense?

Jason_Glass_2L
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Re: Tips on drawing Lewis structures

Postby Jason_Glass_2L » Sun Nov 29, 2020 8:33 pm

LeanneBagood_2E wrote:To add on to this, are there any Lewis structures that you all think we should all be pretty solid with? Like not necessarily know them by heart but be able to do them with ease if that makes sense?


The lewis structures we should be probably be able to do by ease are lewis structures similar to those for O3 and CO3 2-. They are more complex than the structures for things like CH4 but are still simple to do.

Annette Fishman
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Re: Tips on drawing Lewis structures

Postby Annette Fishman » Sun Nov 29, 2020 9:56 pm

Best advice is to count the electrons first in order to fill the octets for all the atoms (as they are most stable that way).

dana hu 1B
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Re: Tips on drawing Lewis structures

Postby dana hu 1B » Sun Nov 29, 2020 9:57 pm

Step 1: Find the Total Number of Valence Electrons. In this step, add up the total number of valence electrons from all the atoms in the molecule.
Step 2: Find the Number of Electrons Needed to Make the Atoms "Happy".
Step 3: Determine the Number of Bonds in the Molecule.
Step 4: Choose a Central Atom.
Step 5: Draw a Skeletal Structure.

Susan Chamling 1F
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Re: Tips on drawing Lewis structures

Postby Susan Chamling 1F » Mon Nov 30, 2020 12:03 am

Hi! I sometimes have difficulty drawing Lewis Structures too, but what I do to prevent errors is that I always check I have the correct number of electrons that includes the valence electrons of the atoms as well as the charge if applicable. Another thing that helps is noticing how the formula is written, as this can sometimes hint to how the atoms are placed in the Lewis structure. I also try to remember that the atom with the least amount of ionization energy is typically placed in the center.

Fernanda Olvera 3D
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Re: Tips on drawing Lewis structures

Postby Fernanda Olvera 3D » Mon Nov 30, 2020 12:05 am

I agree with Dana!
For me it really helps to count the electrons first and then I try to follow the octet rule.

MichaelRaad_1F
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Re: Tips on drawing Lewis structures

Postby MichaelRaad_1F » Mon Nov 30, 2020 1:30 am

I write out the number of valence electrons and learn how to recognize the number of bonds elements tend to form. For example carbon tends to form 4 bonds while oxygen tends to form two bonds based off of the electrons in their valence shell.

Linette Choi 3L
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Re: Tips on drawing Lewis structures

Postby Linette Choi 3L » Fri Dec 11, 2020 2:29 pm

I first count up all of the electrons, so for instance, if the molecule was AlCl3, I would have 24 electrons (3 + 3*7). Then, I draw out the structure, keeping the oxidation states in mind. So since Cl has an oxidation state of 1- and Al has one of 3-, I would deduce that Al would have 3 single bonds to satisfy Cl. After drawing in the bonds, I would then use the leftover electrons as lone pairs on the Cl and Al. Finally, I would then see if I could draw any resonance structures, and use formal charge to find the structure with the lowest charge.

Simi Kapila_3E
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Re: Tips on drawing Lewis structures

Postby Simi Kapila_3E » Fri Dec 11, 2020 2:41 pm

Make sure you count up all of your valence electrons on your atoms in the molecule. Then add any electrons if you have anion (the number of electrons you add is equal to the charge of your anion) or subtract any electrons if you have a cation (again the number of electrons you remove is equal to the charge of your cation). Once you total up your valence electrons, you know how many you should have in your final molecule. When you draw it, usually the atom with the highest electronegativity will be the central atom (H will never be a central atom). And after you draw your molecule, check the formal charge of each atom to see if you the sum of all your charges is equal to the overall charge of your molecule, and see if you can find a better structure with formal charges closer to zero.

Brianne Conway 1D
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Re: Tips on drawing Lewis structures

Postby Brianne Conway 1D » Fri Dec 11, 2020 5:15 pm

Selena Quispe 2G wrote:Hi! So I like to calculate how many valence electrons I should have and then count the electrons again to make sure that I have drawn the lewis structure correctly. Also calculate the formal charges and remember you want the most stable/less charged structure. However, if you do have a charge like let's say a negative charge remember that the element that is the most electronegative will want to have that charge like for example the halogen group. Also memorize that carbon will form 4 bonds, oxygen prefers a double bond, nitrogen will want to form a triple bond, and halogens like to form one bond. I hope this helps!!


Yup, I do the same thing. I would say the most important things are making sure you have the right number of electrons and the lowest possible formal charges.

705512695
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Re: Tips on drawing Lewis structures

Postby 705512695 » Fri Dec 11, 2020 6:39 pm

I find that remembering how many bonds an atom likes to from (B=3, C=4, 0=2, H=1...etc) really helps me break down a large structure.

DominicMalilay 1F
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Re: Tips on drawing Lewis structures

Postby DominicMalilay 1F » Sat Dec 12, 2020 10:21 pm

I make sure to count the electrons and remember that the charge of the overall molecule matters for adding/subtracting electrons!

Brandon Carris
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Re: Tips on drawing Lewis structures

Postby Brandon Carris » Tue Dec 15, 2020 6:30 pm

First I like to determine the total number of valence electrons. Then you can map out which bonds you will use and make sure the total number of bonds and lone pairs equals the total valence electron number.

Melanie Krahn 1C
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Re: Tips on drawing Lewis structures

Postby Melanie Krahn 1C » Tue Dec 15, 2020 7:44 pm

My steps for drawing a Lewis Structure generally look something like this:

1. Finding the number of valence electrons from each atom in the molecule and add them together.
2. Calculate the number of lone pair electrons
3. Determine the number of electrons needed to make the molecule the most stable.
4. Find the number of bonds required.
5. Select the central atom, I believe it's typically the atom with the lowest subscript or the most stable one
6. Draw your lewis structure.
7. Calculate and assign formal charges

205323697
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Re: Tips on drawing Lewis structures

Postby 205323697 » Thu Dec 17, 2020 8:12 am

I notice that sometimes we will have a double bond instead of a single bond and in other cases we would keep all single bonds and draw out the other love pair electrons. I know that creating double bonds makes the molecule more stable, but how do we know when to do that?


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