octet exceptions

[Aashka Popat 1A]

What elements do the exceptions to the octet rule apply to and why is this able to happen?

[Robin Cadd 1D]

The only elements that hold stead-fast to the octet rule are C, N, O, F, and Ne. Hydrogen and helium will always have less than an octet (precisely, 2 electrons) because of the number of electrons their orbitals are able to accommodate. As a general rule, elements in the p-block with shell n=3 or greater will be able to accommodate more than 8 electrons because of their unfilled d-subshell. Hope this helps.

[Wendy 1E]

Boron is also an exception to the octet rule as it can be content with 6 valence electrons, instead of an octet.

[Sion Hwang 4D]

Elements that are period 3 and beyond in the periodic table have access to the d-orbitals, which can fill up to 10 extra valence electrons. One example of this is SF6, where sulfur has 6 bonds to each fluorine atom and thus has 12 valence electrons.

Some elements, such as B and Al can have incomplete octets because they can be relatively stable with only 6 valence electrons.

Hydrogen and beryllium are also exceptions to the octet, as they have too few electrons to complete an octet.

[Sharon Rodriguez 3H]

Elements that are period 3 and beyond in the periodic table have access to the d-orbitals, which can fill up to 10 extra valence electrons. One example of this is SF6, where sulfur has 6 bonds to each fluorine atom and thus has 12 valence electrons.

Some elements, such as B and Al can have incomplete octets because they can be relatively stable with only 6 valence electrons.

Hydrogen and beryllium are also exceptions to the octet, as they have too few electrons to complete an octet.

Why are B and Al realtively stable with only 6 while others require an octect?

[Maddie]

I would also note to be mindful of this exception especially when writing the electron configuration for Cu and Cr

[MeeraBhagat]

Elements in the third energy level and higher can have more than an octet. This is because they have empty d orbitals available to hold the extra electrons.

[Emil Velasco 1H]

Usually any element under the 3rd period may have an expanded octet due to having the whole of the d-block possible in their electron configuration

[AniP_2D]

C, N, O, F, and Ne are the main elements that must follow the octet rule. There are elements like hydrogen that only need two and those like boron that need 6. Also any element past phosphorus can hold more than 8 electrons.

[Rohan Kubba Dis 4B]

There are many octet exceptions. First, H only needs one electron to complete its shell, and this extends to He and a couple of other elements. Next, we have expanded octets which can be any element in the third period which includes P, S, and Cl. Moreover, then we have radicals and biradicals. Although this is a very rudimentary definition of radicals, the basic ideas is that you have an odd number of electrons or you have two single electrons where a pair should be. In any case, if you have an odd number of electrons, completing the octet may not be achievable. In essence, you do the most you can and give any (leftover) electrons to the most electronegative element.

[SarahCoufal_1k]

Basically most elements in period 3 and beyond. This is because there is now the D sub shell that can be filled. In addition Boron can be satisfied with either 8 or 6 electrons.

[Merin Padayatty 3G]

All elements in period 3 and after can have an expanded octet.