Final answer:
Electron and molecular geometries are determined based on the number of electron groups and lone pairs around a central atom. For instance, a molecule with three bonding groups and one lone pair has a tetrahedral electron group geometry and a trigonal pyramidal molecular geometry.
Step-by-step explanation:
The electron and molecular geometries for molecules with different numbers of electron groups and lone pairs are described using the VSEPR theory. The shapes are defined by the electron group geometry, which includes all electron regions (bonding and non-bonding), and the molecular geometry, which includes only the positions of the atoms.
- (a) Four electron groups overall; three bonding groups and one lone pair: Electron group geometry is tetrahedral; molecular geometry is trigonal pyramidal.
- (b) Four electron groups overall; two bonding groups and two lone pairs: Electron group geometry is tetrahedral; molecular geometry is bent or angular.
- (c) Five electron groups overall; four bonding groups and one lone pair: Electron group geometry is trigonal bipyramidal; molecular geometry is seesaw.
- (d) Five electron groups overall; three bonding groups and two lone pairs: Electron group geometry is trigonal bipyramidal; molecular geometry is T-shaped.
- (e) Five electron groups overall; two bonding groups and three lone pairs: Electron group geometry is trigonal bipyramidal; molecular geometry is linear.
- (f) Six electron groups overall; five bonding groups and one lone pair: Electron group geometry is octahedral; molecular geometry is square pyramidal.
- (g) Six electron groups overall; four bonding groups and two lone pairs: Electron group geometry is octahedral; molecular geometry is square planar.