Octet Exceptions

[Karina Rodriguez 2H]

How can you tell when there will be an exception to the octet rule and what do you do to accommodate the exception?

[Jade_Tai_2L]

In Lavelle's lectures, he talked about radicals (compounds w/ unpaired e-) and lewis acids/bases that were exceptions to the octet guideline (lecture 15). with Lewis/base reactions, a coordinate covalent bond will form when another atom provides both e- to the lewis acid molecule.

[Brittney Nguyen 2L]

Hi!

Elements in the p block that have an empty d orbital to fill can have an expanded octet. For example, xenon has the electron configuration. [Kr] 4d^10 5s^2 5p^6. Note that the 5d orbital isn't filled for xenon, so xenon has the potential to have more than 8 electrons in its outer shell, like it does in XeF_2.

The first four elements on the periodic table (H, He, Li, Be) will usually only have 2 valence electrons in its outer shell.

For compounds with an odd amount of electrons, the more electronegative atom will have a full octet, while the less electronegative atom will be a radical. For example, the N in NO has only 7 valence electrons, while the O has 8.

I think those are all of the rules.

I don't really know what you mean by "accommodate the exception." Could you elaborate?

[Andre Fabian 1F]

Hi there!

Octet exceptions occur for elements that contain d-block electrons (i.e. in and past the third period on the periodic table). My interpretation of "accommodating" would mean when would we use this rule? Normally, we would use the expanded octet in order to ensure the stability of a molecular structure. Using a double bond in place of a single bond could decrease the amount of formal charges spread throughout the atom, thus increasing stability of the overall molecular structure.


Hope this helps!

[Sharon Kim 2A]

We know that there are octet exceptions starting from the 3rd p-block. An element that is able to attain a d-orbital usually starting from P and on are expanded octets. Elements that have less than an octet would be Group 13 elements, radicals, H, He, Li, and Be.

[Maddie Turk Disc 2J]

Why can Xe hold more than 8 electrons?

[Eunice_Castro_1G]

Hi! The octet executions include group 13, which don't often complete the octet guideline, this is because they are basically in the middle and would need 5 electrons! Starting with period 3 and below, these elements can have an extended octet due to the d orbital. Hope this helps!

[Eunice_Castro_1G]

Why can Xe hold more than 8 electrons?

This is because as I said in my last post, the d-orbital can accommodate more than 8 electrons. Hope this helps!

[Sharon Kim 2A]

Elements starting from the 3p orbital on and elements that are able to have d-orbitals can have expanded octets. Elements that have less than octets are Group 13 elements common ones are (Al, B), free radicals (CH3), any sort of Lewis acid/base molecules. Hope this helps!

[Mauricio Maravilla 3C]

Usually you will see Sulfur and Phosphorus forming expanded octets, and sometimes it can be some of the halogens, and even noble gases. The best way to figure out if something has an expanded octet is to try and draw it's Lewis structure.

[205323697]

Sometimes I saw an atom bonding with five other atoms, how does this happen and what other atoms have the same behavior where they have their octet of 10.

[Minoo Bastani 2J]

The way that you are able to determine if an atom will have an expanded octet is to see if it has available d- or f-orbitals because that means that it can have more than 8 valence electrons, hence giving it that expanded octet.