You need to identify the domains of the molecule. The electron domains is what shapes the atom. Nh3 has three electron domains with a geometry of spherical with two different electron configurations. The electron domain for NH3 are spherical with two different configurations and it’s trigonal bipyramidal configuration have a geometry of sp3 hybridization and this is how you determine an atom type in an electronic structure by identifying or recognizing these types of geometries like that sp3 hybridized.