Question

By examining electron domain geometry, one can determine that the ammonia molecule (NH3) has

Answer 1

has only one sp2 orbitals, 

Only one sp2 shell is filled up because it ammonia has only 5 valence electrons. Considering ammonia's trigonometrical pyramid shape, 3 hydrogen atoms are attached to Nitrogen. A lone pair remains unattached to any other atom and results to hybridization of sp3 orbitals.