When a lone pair is involved in a dative covalent/ coordinate bond with another atom is it then considered as a bonding pair (when considering the shape of the moelcule?)
For example I thought the F-B-F angle in H3NBF3 would be 107 (trigonal) because there are 3 bonding pairs around the central B atom, and one lone pair, however it is 109.5, implying a tetrahedral shape and that the central atom has 4 bonding pairs around it.
I hope that makes sense!