General principles of octet exception

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Ziyan Wang 3J
Posts: 51
Joined: Wed Sep 18, 2019 12:22 am

General principles of octet exception

Postby Ziyan Wang 3J » Thu Nov 07, 2019 10:31 am

What is the general principles of when we should conform octet rule and when not?

Audrie Chan-3B
Posts: 50
Joined: Thu Jul 25, 2019 12:17 am

Re: General principles of octet exception

Postby Audrie Chan-3B » Thu Nov 07, 2019 11:14 am

P, S, and Cl can have expanded octets, but generally all the elements before it must abide by the octet rule.

Jasmine Fendi 1D
Posts: 108
Joined: Sat Aug 24, 2019 12:15 am

Re: General principles of octet exception

Postby Jasmine Fendi 1D » Thu Nov 07, 2019 11:18 am

I think that everything in row 3+ can have an expanded octet, and elements such as Aluminum does not have to have an octet.

Michelle Xie 2B
Posts: 99
Joined: Sat Aug 17, 2019 12:18 am

Re: General principles of octet exception

Postby Michelle Xie 2B » Fri Nov 08, 2019 12:57 am

Atoms with n=3 and greater can accommodate more than 8 electrons in its valence shell.

andrewcj 2C
Posts: 102
Joined: Thu Jul 11, 2019 12:17 am

Re: General principles of octet exception

Postby andrewcj 2C » Fri Nov 08, 2019 2:17 am

The expanded octet comes from access to d orbitals, which can be used to create additional bonds to the 4 allowed by the s and p orbitals. In general, if an atom in a molecule can achieve a lower formal charge and make the molecule have a more logical formal charge by making more than 4 bonds (therefore violating the octet rule), it will.

Anish Patel 4B
Posts: 59
Joined: Thu Jul 11, 2019 12:17 am

Re: General principles of octet exception

Postby Anish Patel 4B » Fri Nov 08, 2019 10:26 am

Here is what I wrote down in my notes:
Less than 8 e-: H, B, He, Be (Aluminum and Boron only need 6 valence electrons)
More than 8 e-: P, S, Cl, Xe and below

Sofia Barker 2C
Posts: 101
Joined: Wed Sep 18, 2019 12:21 am

Re: General principles of octet exception

Postby Sofia Barker 2C » Sun Nov 10, 2019 1:43 pm

In general, H, He, and Li want 2 electrons because that satisfies the 1s orbital. Elements in period 3 and any period after can accommodate more than 8 valence electrons because of the d orbitals. Always check formal charge when drawing Lewis structures to confirm that the structure you have drawn is the most stable; this is the best way to prove whether or not the octet rule should apply or not.

gabbymaraziti
Posts: 111
Joined: Wed Sep 18, 2019 12:19 am

Re: General principles of octet exception

Postby gabbymaraziti » Sun Nov 10, 2019 1:45 pm

When a central atom has empty d-orbitals close in energy to valence orbitals, it can accommodate an expanded octet. Basically, atoms in the p-block of period 3+ can accommodate an expanded octet, but the size of the central atom also matters. It has to be physically capable of forming bonds to more extra atoms.


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