Octet Rules

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Cassidy Kohlenberger 3D
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Joined: Wed Sep 18, 2019 12:19 am

Octet Rules

Postby Cassidy Kohlenberger 3D » Fri Nov 01, 2019 8:25 pm

What is the difference between an element that does not have to satisfy the octet rule, and an element that can have an extended octet? I think, I might be wrong, that all elements group 3 and below can have an extended octet?

Lauren Bui 1E
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Joined: Sat Jul 20, 2019 12:15 am

Re: Octet Rules

Postby Lauren Bui 1E » Fri Nov 01, 2019 8:59 pm

If an atom does not satisfy the octet rule, it means there are less than 8 electrons (i.e. the first 4 elements of the periodic table). An expanded octet refers to when there are more than 8 electrons; these are also known as exceptions to the octet rule.

Rebekah Alfred 1J
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Re: Octet Rules

Postby Rebekah Alfred 1J » Fri Nov 01, 2019 9:03 pm

In the review session today, it was mentioned that the elements (with a d-orbital) in Period 3 and later can have an expanded octet.

Rebekah Alfred 1J
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Re: Octet Rules

Postby Rebekah Alfred 1J » Fri Nov 01, 2019 9:05 pm

Lauren Bui 1E wrote:If an atom does not satisfy the octet rule, it means there are less than 8 electrons (i.e. the first 4 elements of the periodic table). An expanded octet refers to when there are more than 8 electrons; these are also known as exceptions to the octet rule.


Examples of elements that typically have less than an octet/do not satisfy the octet rule (as Lauren mentioned) are Hydrogen, Helium, Lithium, and Beryllium. Examples of elements that can have an expanded octet are Phosphorus, Sulfur, and Chlorine.

Katie Kyan 2K
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Re: Octet Rules

Postby Katie Kyan 2K » Fri Nov 01, 2019 9:19 pm

Elements that can have expanded octets are the elements in row 3 and beyond. If we look at the principal quantum number for period 3 elements (n=3), we see that the angular momentum number can be all values up to n-1. This means that the angular momentum number can take on the values of 0,1, or 2. Since l=2 corresponds to the d-orbital and the elements in period 3 don't have any electrons in this orbital, these elements and those beyond can have an expanded octet. The elements that do not have a full octet are H, He, Li, and Be. Elements in the column of Boron can have either an expanded octet or a not filled one.


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