Which of the following molecules has trigonal planar geometry ?

To determine the molecular geometry of a molecule, we need to analyze the number of electron groups around the central atom and the number of bonding groups. So, let's consider each option: option 1 involves IF3, option 2 involves PCl3, option 3 involves NH3, and option 4 involves BF3. Notice that BF3 has a trigonal planar geometry, with three bonding groups and no lone pairs around the central atom. Think of it this way: the molecular geometry of a molecule is determined by the number of electron groups around the central atom, and the number of bonding groups. In other words, the molecular geometry is determined by the arrangement of electron groups and bonding groups around the central atom. Therefore, the correct answer is the option that involves a molecule with a trigonal planar geometry, which is option 4.