Describe the shapes of `BF_3` and `BF_4^_`

Explanation

Hybridisation of B in `BF_3 : 1/2 (3+3-0+0)=3 i.e. sp^2`
Hybridisation of B in BH_4: 1/2 (3+4-0+1)=4 i.e. sp^3`
So `BF_3` is trigonal planar and `BH_4` is tetrahedral.