Which molecule has a trigonal planar geometry? A. I{F_3}B. PC{l_3}C. N{H_3}D. B{F_3}

To determine which molecule has a trigonal planar geometry, we need to consider the VSEPR theory (Valence Shell Electron Pair Repulsion theory), which helps predict the shape of a molecule based on the number of bonding and non-bonding electron pairs around the central atom.
Step 1: Analyze the Given Molecules
1. IF₃ (Iodine trifluoride):
o Central atom: Iodine (I)
o Iodine has 7 valence electrons, and with 3 fluorine atoms bonded, there are 2 lone pairs of electrons on iodine.
o Electron geometry: Due to the presence of 3 bonding pairs and 2 lone pairs, the electron geometry is trigonal bipyramidal. However, the molecular geometry is T-shaped, not trigonal planar.
2. PCl₃ (Phosphorus trichloride):
o Central atom: Phosphorus (P)
o Phosphorus has 5 valence electrons, and with 3 chlorine atoms bonded, there is 1 lone pair of electrons on phosphorus.
o Electron geometry: The electron geometry is trigonal pyramidal because of the 3 bonding pairs and 1 lone pair. The molecular geometry is also trigonal pyramidal, not trigonal planar.
3. NH₃ (Ammonia):
o Central atom: Nitrogen (N)
o Nitrogen has 5 valence electrons, and with 3 hydrogen atoms bonded, there is 1 lone pair of electrons on nitrogen.
o Electron geometry: The electron geometry is tetrahedral, but the molecular geometry is trigonal pyramidal, not trigonal planar.
4. BF₃ (Boron trifluoride):
o Central atom: Boron (B)
o Boron has 3 valence electrons, and with 3 fluorine atoms bonded, there are no lone pairs on boron.
o Electron geometry: The electron geometry is trigonal planar because there are 3 bonding pairs and no lone pairs. The molecular geometry is also trigonal planar.
Step 2: Conclusion
The molecule with trigonal planar geometry is BF₃ because:
• It has 3 bonding pairs and no lone pairs on the central atom (boron).
• The electron geometry and molecular geometry both are trigonal planar.
Answer:
D) BF₃\boxed{D) \, \text{BF₃}}