The molecules BF3 and SO3 are both described as trigonal planar. Does this information completely define the bond angles of these molecules?

Question

The molecules BF3 and SO3 are both described as trigonal planar. Does this information completely define the bond angles of these molecules?What is the difference between the electron-domain geometry and the molecular geometry of a molecule? Use ammonia molecule as an example in your discussion.

c. Acetone, C3H6O, is commonly used as organic solvent that is the main component of some nail-polish removers. Its Lewis structure shows the following connectivity CH3-CO-CH3

i. What is the total # of valence electrons in the acetone molecule?

ii. How many valence electrons are used to make sigma bonds in the molecule

iii. How many valence electrons are used to make pi bonds in the molecule?

iv. How many valence electrons remain in non-bonding pairs in the molecule?

v. What is the hybridization at the central carbon atom of the molecule?

Answer 1

Yes, BF3 and SO3 are trigonal planar with a bond angle of 120 degrees. They are non-polar.

Ammonia has a tetrahedral electron geometry but a trigonal pyramidal molecular geometry (which is a more accurate representation of the molecule) because the lone pair of electrons repel the bonding electrons more since they are closer to the nitrogen atom than the bonding electrons. This causes the the tetrahedral to be "bent" into a trigonal pyramidal shape (the bonds are closer together). This forms bond angles slightly less than the usual 109.5 degree bond angles of a tetrahedral.

All of the bonds in acetone are sigma bonds except for the pi bond which is one of the bonds in the double bond between the central carbon and the oxygen. The pi bond results from a lateral overlap between one of the 2p orbitals in carbon and one of the 2p orbitals in oxygen. The sigma bonds result from a head-on overlap of orbitals. The central carbon is sp2 hybridized having 3 electron groups.