Answer
See the explanation
Work Step by Step
For the molecules in Exercises 27 and 28:
The expected hybridization of the central atom is sp2.
In Exercise 27, the molecule is borane (BH3). The boron atom in the center is bonded to three hydrogen atoms, forming a trigonal planar arrangement. This requires the boron atom to have an sp2 hybridization, where the s orbital and two p orbitals combine to form three equivalent sp2 hybrid orbitals.
In Exercise 28, the molecule is ethylene (C2H4). The carbon atoms in the center are each bonded to two hydrogen atoms and another carbon atom, forming a trigonal planar arrangement. This requires the carbon atoms to have an sp2 hybridization
