Is there any change in the hybridisation of B and N atoms as a result of the reaction?
In ${ BF }{ 3 }$, there are 3 bond pairs 0 lone pair, so boron is sp2 hybridised and in
${ NH }{ 3 }$, there are 3 bond pairs and 1 lone pair, so nitrogen is sp3 hybridised. After the reaction hybridisation of boron changes to ${{sp}^{3}}$ but hybridisation of nitrogen remains the same because N shares its lone pair with electron deficient B.