Octet Rule

[IsabelMurillo3K]

When listening to the lecture, professor mentioned that the exceptions to the octet rule include H, He, Be, and Li. I was wondering if anyone could explain why these are exceptions to the octet rule. Is it because of the low number of valence electrons? Thanks in advance!

[Chance Herbert 3A]

For hydrogen, the octet rule does not apply since the atom can only have a maximum of two electrons in its outermost/valence shell! All successive levels can have a maximum of 8 with the exceptions you listed.

[Isabella Cortes 2H]

The reason that these elements are exceptions to the octet rule is that they can only have a maximum of 2 valence electrons

[Neel Sharma 3F]

Valence electrons are a big part of the reason they do not need to have an octet in bonding. Looking at the periodic table we can see that B and Al are in the np^1 configuration. This makes it harder for them to gain enough 8 electrons and instead they often bond with 6. Also, the octet rule is not a strict guideline that will always be followed. It is just a pattern that is based on trends seen in bonding. We see elements with expanded octets as well. Hope this helps!

[Lauren Sarigumba 1K]

H, He, Li, and Be are exceptions to the octet rule because their electron configurations do not reach the 2p orbitals. This means that they only have the 1s and 2s orbitals and do not have the capacity to have 8 electrons in their valence shells.

[Mrudula Akkinepally]

Hi! They are exceptions to the octet rule because of their limited number of valence electrons.

[Savannah Torella 1L]

As mentioned above, H, He, Li, and Be are exceptions to the octet rule because they only consist of the s-orbital. Since H and He only contain the 1s orbital, and Li and Be only contain the 1s and 2s orbitals, none of these elements can hold 8 valence electrons. Without containing the p orbitals, these elements have no way of reaching the full 8 valence electrons, so that excludes them from the octet rule.