What is the molecular geometry of a molecule with a steric number of 5 and 2 lone pairs? trigonal bipyramidal bent T-Shaped trigonal bipyramidal tetrahedral
The correct answer and explanation is:
The correct molecular geometry for a molecule with a steric number of 5 and 2 lone pairs is T-shaped.
Explanation:
The steric number is the total number of regions of electron density around the central atom, which includes both bonding pairs and lone pairs of electrons. In this case, a steric number of 5 means there are five electron groups around the central atom.
When there are no lone pairs, five electron groups arrange themselves in a trigonal bipyramidal electron geometry. This shape has three positions in an equatorial plane, 120 degrees apart, and two positions axial, 180 degrees apart, perpendicular to the equatorial plane.
If two of these five groups are lone pairs, the shape of the molecule changes because lone pairs repel bonding pairs more strongly than bonding pairs repel each other. Lone pairs prefer to occupy the equatorial positions in a trigonal bipyramidal arrangement to minimize repulsion.
With two lone pairs, the molecule keeps three bonding pairs around the central atom. The lone pairs occupy two equatorial positions, and the three bonded atoms take the remaining positions, which result in a T-shaped molecular geometry.
This T-shaped geometry looks like the letter T, with the three bonded atoms positioned in a way that forms a shape similar to the letter T. The bond angles are slightly less than 90 degrees due to lone pair repulsion compressing the angles between bonding atoms.
Other options explained:
- Trigonal bipyramidal refers to the electron geometry with five bonding groups and no lone pairs.
- Bent geometry is typical for molecules with a steric number of 3 or 4 with lone pairs, not 5.
- Tetrahedral geometry applies to steric number 4 with no or one lone pair, not 5.
Thus, for steric number 5 with two lone pairs, the correct molecular geometry is T-shaped.