Boron and aluminum exception

[Nicole Ju 3H]

I am kind of confused on the exception for boron and aluminum. If I'm correct in my understanding, Boron can be stable with just 6 valence electrons, but it can also act as a Lewis acid and accept an electron pair to form an octet? So does this mean Boron also follows the octet rule? Also, does aluminum act the same way as Boron in this sense?

Thanks!

[Neelaj Das 3I]

So yes, boron is capable of forming a stable structure with an incomplete octet (only 6 valence electrons) and aluminum also behaves in this manner. However, if the necessary conditions are present, molecules with boron such as BCl3 can act as lewis acids and accept a lone pair of electrons from another atom or molecule, giving boron a complete octet. Same concept applies to aluminum.

[Mihir Sukhatme 1D]

Yes, technically they follow both rules. They can be stable with only 6 electrons, but if the proper conditions are met then they can also exist with the octet rule and form bonds to get to 8 electrons.