Trigonal Planar Molecules
(a) Boron trifluoride, BF3
. Its Lewis structure shown that the central atom B has three bonding
electron pairs and no unshared electrons. VSEPR theory says that the three bonding electron pairs
will be as far apart as possible. This can be so if these electron pairs are directed to the corners of an
equilateral triangle. Thus VSEPR model of BF3molecule has three F atoms at the corners of the triangle
with B atom at its centre. All the four atoms (three F and one B) lie in the same plane. Therefore, the
shape of such a molecule is called trigonal planar. The bond angle is 120º.