Lewis Structures

[aaronharouni]

Why does the B in BF3 only have 6 electrons in its Lewis structure?

[Brian Cook]

Boron doesn't need a full octet because it's in the 13th column, and elements there have stable electron states already.

[megan blatt 2B]

Boron is an exception to the octet rule. This occurs because a coordinate covalent bond is formed. In coordinate covalent bonds, one of the two atoms involved in the bond provides both of the shared electrons as opposed to each atom involved in the bond providing one electron. Additionally, if you were to calculate Boron's formal charge in a molecule like BF3, it would equal zero. Therefore, you know that even without an octet, Boron is stable in this molecule.

[Manya Bali 4E]

What's already been said is true, but I also wanted to add that it's possible for B (boron) to complete its octet if another atom provides two electrons in what's called a coordinate covalent bond. To reiterate the example from today's lecture, BF3 + F^- --> BF4^-. In the product, B forms an octet due to the two electrons given by F^- (remember that F^- has 8 valence electrons).

[Javier_Ochoa_DIS_3J]

Any element in the 13th column does not need to have a full octet. This would include B, Al, Ga, In, Ti, and Nh.

However they are allowed to have 8 if the compound needs it.