When boron trifluoride forms and adduct with ammonia , what are the changes in the hybridisation and geometry?

Explanation

Hybridisation of boron in `BF_3` is `sp^2` with one empty p-orbital in valence shell. When it forms an adduct with ammonia, boron extends its co-ordination number from three to four by using its empty p-orbital.
The hybridisation of boron changes to `sp^3` and geometry becomes tetrahedral In ammonia, the hybridisation of nitrogen remains as `sp^3` but geometry changes from pyramidal to tetrahedral.