Which of the following statements correctly distinguishes between trigonal planar and trigonal pyramidal molecular geometries?

• A. Trigonal planar molecules have one lone pair on the central atom, while trigonal pyramidal molecules have no lone pairs.
• B. Trigonal planar and trigonal pyramidal molecules both have bond angles of 120 degrees.
• C. Trigonal planar molecules have all atoms in the same plane and no lone pairs on the central atom, while trigonal pyramidal molecules have one lone pair on the central atom and atoms are not all in the same plane.
• D. Trigonal pyramidal molecules are always nonpolar, while trigonal planar molecules are always polar.

Answer: (C)

Verified step by step guidance

1. Understand the definitions of the two molecular geometries: trigonal planar and trigonal pyramidal.
2. Recall that trigonal planar geometry involves a central atom bonded to three atoms with no lone pairs, resulting in all atoms lying in the same plane and bond angles of approximately 120 degrees.
3. Recognize that trigonal pyramidal geometry involves a central atom bonded to three atoms but with one lone pair, causing the molecule to have a three-dimensional shape where atoms are not all in the same plane and bond angles slightly less than 109.5 degrees due to lone pair repulsion.
4. Compare the presence or absence of lone pairs and the spatial arrangement of atoms in both geometries to distinguish them correctly.
5. Evaluate the given statements based on these characteristics to identify which one accurately describes the difference between trigonal planar and trigonal pyramidal molecular geometries.