Final answer:
The term “trigonal pair” is likely a typo for “trigonal pyramidal”, and none of the options provided in the question correctly describe a molecule or ion with this shape.
Step-by-step explanation:
The student is asking about the shape of a specific molecule or ion with a “trigonal pair” shape. This term is likely a mistake, and the student means “trigonal pyramidal” shape. Based on the information provided, option (d) ClO₄⁻ does not have a trigonal pyramidal shape but actually has a tetrahedral electron-pair geometry, with a molecular structure that is closer to trigonal pyramidal due to the presence of lone pairs affecting the shape. However, the correct terminology to define the geometry of a molecule with three bonds and one lone pair, like the ClO₄⁻ ion, would refer to the molecular shape as “trigonal pyramidal.” Options (a) H₂S and (b) PCl₅ do not have the required trigonal pyramidal shape either. The correct answer is not listed among the options provided, as none of them perfectly correspond to a trigonal pyramidal shape with a lone pair on the central atom.
The molecule or ion that has a trigonal pyramidal shape is PCl₅.