Final answer:
Water (H₂O) has a bent molecular shape, and ammonia (NH₃) has a trigonal pyramidal molecular shape.
Step-by-step explanation:
The names of the molecular shapes of water, H₂O, and ammonia, NH₃, reflect their geometric configurations.
The shape of a water molecule is called bent or angular, where the two hydrogen atoms are attached to the oxygen atom at an angle with two lone pairs of electrons on the oxygen, resulting in a V-shaped structure lying in a plane.
For ammonia, the molecular shape is known as trigonal pyramidal, with nitrogen at the vertex and the three hydrogen atoms forming the base of the pyramid; this geometry arises because the nitrogen has one lone pair of electrons in addition to the three bonded hydrogen atoms.