Final answer:
The shape of a molecule with double or triple bonds is influenced by the number of electron groups and can be bent, planar, or trigonal planar.
Step-by-step explanation:
The shape of a molecule that includes a double or triple bond depends on the number of electron groups around the central atom. If we consider formaldehyde (CH2O), which has a double bond between carbon and oxygen, the electron groups around the central carbon atom are arranged in a tetrahedral geometry. However, since one of these groups is a double bond, and there are no nearby competing atoms, the shape of the molecule is considered bent or angular. This is because the double bond counts as one electron group.
In a molecule like ethene (C2H4), which has a double bond between two carbon atoms, the molecular shape is planar, or flat, because double bonds can't rotate and lock the structure in place. For a molecule like Boron trifluoride (BF3), which has three electron groups, the molecular shape is trigonal planar, resembling an equilateral triangle. This is due to the three electron groups wanting to be as far apart as possible, adopting positions 120° apart within a plane.
In summary, molecules with double or triple bonds can have shapes like bent, planar, or trigonal planar depending on the arrangement and number of electron groups around the central atom.