Question

how many pairs of bonding electrons are present in a molecule that displays a trigonal bipyramidal molecular shape?
5
3
4
6

Explanation:

Step1: Recall VSEPR theory

The trigonal bipyramidal molecular shape is determined by the number of bonding electron pairs (and lone pairs) around the central atom. For a trigonal bipyramidal shape, the electron - pair geometry (and molecular shape, assuming no lone pairs) corresponds to 5 bonding electron pairs. This is because the trigonal bipyramidal geometry has 5 regions of electron density, which in the case of all bonding pairs (no lone pairs) gives the trigonal bipyramidal molecular shape. For example, in a molecule like \(PCl_5\), the central phosphorus atom has 5 bonding pairs (each with a chlorine atom), resulting in a trigonal bipyramidal shape.

Step2: Evaluate the options

• Option 5: Matches the number of bonding pairs required for a trigonal bipyramidal molecular shape.
• Option 3: A trigonal planar shape (for 3 bonding pairs) is different from trigonal bipyramidal, so this is incorrect.
• Option 4: A tetrahedral shape (for 4 bonding pairs) is different, so this is incorrect.
• Option 6: An octahedral shape (for 6 bonding pairs) is different, so this is incorrect.

Answer:

5