Remember, in a Covalent bond, one electron comes from here, and one electron comes from here. But in this case, both electrons come from a single atom. So let's look at the structural depiction of BF three. BF three has three HS attached to the boron, and the boron has an empty orbital. And this empty orbital is what interacts with the lone pair of electrons on our H, forming our corticovalent bond. So in this case, the BF three accepted the pair of electrons because it had that anti orbital.