Octet Rule

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Kandyce Lance 3E
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Octet Rule

Postby Kandyce Lance 3E » Sun Nov 22, 2020 11:23 pm

I was having some trouble drawing lewis structures recently because I would often find myself with (usually 2) extra electrons. After I had already filled the outer elements to 8. It was in a recent lecture that Dr. Lavelle put the lone pairs on the elements in the middle and I never thought to do that because doesn't that defy the octet rule?

Kandyce Lance 3E
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Joined: Wed Sep 30, 2020 9:46 pm

Re: Octet Rule

Postby Kandyce Lance 3E » Sun Nov 22, 2020 11:24 pm

Kandyce Lance 2L wrote:I was having some trouble drawing lewis structures recently because I would often find myself with (usually 2) extra electrons. After I had already filled the outer elements to 8. It was in a recent lecture that Dr. Lavelle put the lone pairs on the elements in the middle and I never thought to do that because doesn't that defy the octet rule?



Additionally, does the octet rule not apply to the elements with a high ionization level? or is this only acceptable for a few elements?

SophiaBarden 2E
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Re: Octet Rule

Postby SophiaBarden 2E » Sun Nov 22, 2020 11:28 pm

The octet rule would only be "broken" if an atom has more than 8 valence electrons filling its outer orbital. You most make sure you calculate the total electrons involved in a molecule and make sure to calculate the formal charge of each atom. As with every chemistry rule, there are many exceptions. Elements with access the the d orbital (period 3 and above) are able to expand their octet, and have more than 8 valence electrons involved in their outer shell and bonding. Examples of atoms that can expand their octet are P, S, and Cl.

Silvi_Lybbert_3A
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Re: Octet Rule

Postby Silvi_Lybbert_3A » Sun Nov 22, 2020 11:31 pm

I believe the only examples where Dr. Lavelle have added lone pair electrons to the central atom when the atom already has an octet is when that central atom is an element that can have electrons in the d-orbital. For example, when sulfur is the central atom of a molecule and you need a place to put extra electrons without adding bonds to the atoms surrounding the sulfur, then you can put the lone pair on the sulfur atom. The sulfur atom is in row 3 and can have electrons in the d-orbital because shell n=3 can have l=2 which is the d-orbital (3d is in row 4 on periodic table in the d-block). This allows it to have an expanded octet. The octet rule is only a guideline, and comes from elements in rows 1 and 2 with only s and p orbitals (8 electrons can exist in a shell with only s and p orbital).

Natalie 3k
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Re: Octet Rule

Postby Natalie 3k » Sun Nov 22, 2020 11:32 pm

I have this issue a lot too, but I know that the octet rule can be defied for certain elements. In some cases, the d orbitals can accept electrons as well, which allows some elements like sulfur and chlorine to have more than 8. I'm not sure what the exact rules for this are, but hopefully someone else can help!

Jaden Ji 2K
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Re: Octet Rule

Postby Jaden Ji 2K » Sun Nov 22, 2020 11:37 pm

Like what Sophia said, calculating the formal charge and counting the number of electrons around each atom helps in finding the electrons in the middle. I like to see how many valence electrons are needed to fulfill the electrons in the middle and count the bonded electrons as those needed electrons. Then, with the leftover bonded electrons I take them away from the number of valence electrons the element already has, to see how many electrons are left in the middle. I hope this helps!

David Liu 1E
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Re: Octet Rule

Postby David Liu 1E » Mon Nov 23, 2020 9:30 pm

like lavelle said in lecture, I feel like it's important to note that the "normal" elements we use generally follow the trend, but any element that has access to the d orbital past period 3 can generally overcome the octet rule

Rose_Malki_3G
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Re: Octet Rule

Postby Rose_Malki_3G » Tue Nov 24, 2020 1:51 am

Atoms that are in the 3rd row or lower can have more than 8 electrons because they can fill their d states with electrons.

Kimiya Aframian IB
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Re: Octet Rule

Postby Kimiya Aframian IB » Tue Nov 24, 2020 9:35 am

Kandyce Lance 2L wrote:I was having some trouble drawing lewis structures recently because I would often find myself with (usually 2) extra electrons. After I had already filled the outer elements to 8. It was in a recent lecture that Dr. Lavelle put the lone pairs on the elements in the middle and I never thought to do that because doesn't that defy the octet rule?

Hi! For many of the elements there can be an expanded octet on the central atom (usually in elements in and after the 3p block). Also you can try to to undo any double or triple bonds. Hope this helps!

Kendall_Dewey_2D
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Re: Octet Rule

Postby Kendall_Dewey_2D » Tue Nov 24, 2020 8:36 pm

The octet rule is broken when an atom has more than 8 valence electrons filling the outer orbital. Calculating the total electrons involved in a molecule and making sure to include the formal charge of each atom can help with this process. We can't forget about the exceptions to the octet rule, either, Elements from period 3 and above can expand their octet with more than 8 valence electrons in bonding and their outer shell.

isha dis3d
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Re: Octet Rule

Postby isha dis3d » Wed Nov 25, 2020 8:02 am

I had a follow-up question to this discussion thread, is there a maximum number of electrons an expanded octect can accommodate?

America Alvarado
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Re: Octet Rule

Postby America Alvarado » Wed Nov 25, 2020 9:10 am

isha dis1k wrote:I had a follow-up question to this discussion thread, is there a maximum number of electrons an expanded octect can accommodate?

I had read somewhere that it depends on how many orbitals the valence shell of an atom has. If it has more orbitals free then it will be able to accommodate more electrons.
https://chem.libretexts.org/Bookshelves ... oore_et_al.)/07%3A_Further_Aspects_of_Covalent_Bonding/7.02%3A_Exceptions_to_the_Octet_Rule this page explains it better. Hope this helps!

Kelly Tran 1J
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Re: Octet Rule

Postby Kelly Tran 1J » Wed Nov 25, 2020 9:36 am

The octet rule is more of a guideline as there are some exceptions to it. For example, an expanded valence shell is an exception to the octet rule. Atoms in period 3 or higher can accommodate more than 8 valence electrons.

Pranav Daggubati 3C
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Re: Octet Rule

Postby Pranav Daggubati 3C » Wed Nov 25, 2020 10:24 am

Its tricky to consider this. Think of sulfur, it can have six bonds and a lone pair to give it 8 in the valence shell. Remember that covalent bonds are shared. Be careful when thinking that a bond means all the electrons in the bond fulfill an octet. Sulfur, nitrogen and other things can have more than 2 or 3 bonds.

AHUNT_1A
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Re: Octet Rule

Postby AHUNT_1A » Fri Nov 27, 2020 9:45 am

Jaden Ji 3K wrote:Like what Sophia said, calculating the formal charge and counting the number of electrons around each atom helps in finding the electrons in the middle. I like to see how many valence electrons are needed to fulfill the electrons in the middle and count the bonded electrons as those needed electrons. Then, with the leftover bonded electrons I take them away from the number of valence electrons the element already has, to see how many electrons are left in the middle. I hope this helps!



extremely Helpful ! using this as a reference.

Heather Szeszulski 1I
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Re: Octet Rule

Postby Heather Szeszulski 1I » Fri Nov 27, 2020 10:58 am

Another helpful tip my TA told me is to instead think about what electrons have to have an octet and can not go above or below, those elements are C, N, O, F.

Sophia Wendin 3L
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Re: Octet Rule

Postby Sophia Wendin 3L » Fri Nov 27, 2020 11:10 am

Elements in the p-block of period 3 or later have empty d-block orbitals that can hold electrons so they can have more than 8 electrons in their outer shell. S, P, and Cl are some common atoms that can have expanded octets. This confused me at first too!

Kandyce Lance 3E
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Re: Octet Rule

Postby Kandyce Lance 3E » Sun Nov 29, 2020 9:54 pm

David Liu 3B wrote:like lavelle said in lecture, I feel like it's important to note that the "normal" elements we use generally follow the trend, but any element that has access to the d orbital past period 3 can generally overcome the octet rule



Ok great, thank you!


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