Octet Rule Clarification

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Octet Rule Clarification

Postby 104785906 » Tue Jul 18, 2017 11:47 pm

I've seen that many have asked before me and I just want to check my understanding. Essentially any atom, those in period 3 and after that have electrons that start filling the d orbital, can break the octet rule?

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Re: Octet Rule Clarification

Postby Sarah_Wilen » Wed Jul 19, 2017 12:05 am

To my understanding, I believe that any elements in n=3 or beyond can have expanded octets.

In expanded octets, the central atom can have ten e-, even twelve. Molecules with expanded octets involve a nonmetal central atom found in the third period or beyond. While the octet rule is based upon s and p orbitals, beginning with the 3rd period, the d orbitals become available. The third period and beyond elements can exceed the octet rule by using their d orbitals to accommodate the extra electrons.

I didn't include metals in the third period or beyond because, although they do have d subshells, metals tend not to be the central atom in a Lewis structure because metals form ionic bonds giving away their electrons and becoming cations rather than take electrons. They may not have expanded octets because they won't have e- to use in the d subshell. I think. Maybe, someone, should fact check this, but that's what I deduce at the moment.

I guess the most common examples for expanded octets we've seen so far are for sulfer, but there are some other fun examples of elements in n=3 or higher that have expanded octets such as ICl4- and XeF4.

Hope this helps kind of!

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Re: Octet Rule Clarification

Postby mayasinha1B » Wed Nov 01, 2017 12:13 pm

Any element n=3+ can have an expanded octet by utilizing d-orbitals found in the third principal energy level and in higher principle energy levels. Common examples include PCl5 (discussed in class), SF6, ClF3, I3-, etc.

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