Question

Which of the following have a trigonal bipyramidal shape?
\(PF_5, PBr_5, [PtCl_4], SF_6, BF_3, BrF_5, PCl_5, [Fe(CO)_5]\)

• A. \(PF_5, PBr_5, PCI_5, [Fe(CO)_5]\) only
• B. \(PF_5, PBr_5, PCI_5, BrF_5\) only
• C. \(PF_5, PCI_5, [Fe(CO)_5]\) only
• D. \(PF_5, PBr_5, BrF_5, PCI_5, [Fe(CO)_5]\) only

Answer 1

The Correct Option is A

To determine which of the given compounds have a trigonal bipyramidal shape, we need to understand the geometry based on the molecular structure and the concept of VSEPR (Valence Shell Electron Pair Repulsion) theory. A trigonal bipyramidal shape occurs typically in molecules with five bonding regions around the central atom, resulting in angles of 90° and 120° between the bonds.

Let's analyze each compound:

1. PF_5: This compound has five fluorine atoms bonded to phosphorus, with no lone pairs on the central atom, resulting in a trigonal bipyramidal shape.
2. PBr_5: This is similar to PF_5, with bromine atoms instead of fluorine, and also has a trigonal bipyramidal shape.
3. [PtCl_4]: Here, platinum is typically considered to have a square planar geometry, not trigonal bipyramidal.
4. SF_6: This compound has an octahedral shape due to six fluorine atoms bonded to sulfur.
5. BF_3: Boron has three bonding regions which result in a trigonal planar shape, not trigonal bipyramidal.
6. BrF_5: This molecule has a square pyramidal shape due to the presence of lone pairs on bromine, not trigonal bipyramidal.
7. PCl_5: Like PF_5 and PBr_5, this molecule with five chlorine atoms around phosphorus is trigonal bipyramidal.
8. [Fe(CO)_5]: Iron forms a trigonal bipyramidal shape when bonded to five carbonyl groups in this complex.

Among the given options, the compounds PF_5, PBr_5, PCl_5, and [Fe(CO)_5] have a trigonal bipyramidal shape.

Thus, the correct answer is:
PF_5, PBr_5, PCl_5, [Fe(CO)_5] only.