Final answer:
According to VSEPR theory, BH3 has a trigonal planar shape, (NO2)- has a bent geometry, SiH4 is tetrahedral, (CO3)2- is trigonal planar, and SO3 is also trigonal planar, with the shapes determined by electron pair repulsions and the arrangement of atoms to minimize these repulsions.
Step-by-step explanation:
The Valence Shell Electron Pair Repulsion (VSEPR) theory is used to predict the shapes of molecules based on the idea that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion. Here's a summary of the predicted shapes for the given molecules:
- BH3: Boron has three valence electrons and forms three bonds with hydrogen atoms, with no lone pairs. This leads to a trigonal planar geometry with bond angles of 120°.
- (NO2)-: The Nitrite ion has two sigma bonds and one lone pair on the nitrogen, giving rise to a bent geometry with an angle slightly less than 120° due to the presence of the lone pair.
- SiH4: Silicon has four valence electrons and forms four bonds with hydrogen atoms, with no lone pairs. This leads to a tetrahedral shape with bond angles of 109.5°.
- (CO3)2-: The Carbonate ion has three oxygen atoms bonded to a central carbon atom and one lone pair on the carbon, resulting in a trigonal planar geometry with bond angles of 120°.
- SO3: Sulfur trioxide has a similar arrangement to carbonate, with sulfur at the center and three oxygen atoms bonded, but with no lone pairs, also resulting in a trigonal planar geometry with bond angles of 120°.
Note that VSEPR theory only considers electron-pair repulsions. Other factors such as nuclear-nuclear repulsions and nuclear-electron attractions also play a role in determining the final shape of a molecule.