To determine which molecule or ion has a trigonal planar shape, we need to analyze the molecular geometry of the given options. The molecular geometry can be predicted using the Valence Shell Electron Pair Repulsion (VSEPR) theory, which states that electron pairs around a central atom tend to orient themselves as far apart as possible.
Let’s evaluate each option:
A. [tex]\(PCl_5\)[/tex]:
- Phosphorus pentachloride ([tex]\(PCl_5\)[/tex]) has 5 chlorine atoms bonded to a central phosphorus atom.
- According to VSEPR theory, with 5 bonding pairs, [tex]\(PCl_5\)[/tex] adopts a trigonal bipyramidal shape, not trigonal planar.
B. [tex]\(SO_3\)[/tex]:
- Sulfur trioxide ([tex]\(SO_3\)[/tex]) has 3 oxygen atoms bonded to a central sulfur atom.
- There are no lone pairs on the central sulfur atom, which means the electron pairs arrange themselves in a trigonal planar geometry to minimize repulsion.
- Each bond angle is approximately 120 degrees, which is characteristic of a trigonal planar shape.
C. [tex]\(H_2S\)[/tex]:
- Hydrogen sulfide ([tex]\(H_2S\)[/tex]) has 2 hydrogen atoms bonded to a central sulfur atom, along with 2 lone pairs of electrons on the sulfur.
- With 4 regions of electron density, the molecule adopts a bent or V-shaped geometry, not trigonal planar.
D. [tex]\(ClO_4^{-}\)[/tex]:
- The perchlorate ion ([tex]\(ClO_4^{-}\)[/tex]) has 4 oxygen atoms bonded to a central chlorine atom.
- This results in a tetrahedral geometry, with bond angles of about 109.5 degrees, not trigonal planar.
From the analysis above, the correct answer is:
B. [tex]\(SO_3\)[/tex]
[tex]\(SO_3\)[/tex] has a trigonal planar shape with bond angles of approximately 120 degrees.
