Question

A molecule contains three identical polar bonds in a trigonal planar molecular geometry. Is the molecule polar?

Match the words in the left column to the appropriate blanks in the sentences on the right. 

Answer 1

The molecule has polar bonds, the dipole moments of three bonds cancel out because of the trigonal planar geometry,and the molecule is not polar.

In case of poly atomic molecules like AB₃ dipole moment of a molecule is a vector sum of the dipole moments of various bonds.

In AB₃ molecule , A-B bond is polar and shape of molecule is trigonal planar . The shape and bond moments are as shown below.  

t * BE TAZ Bond dipoles (a + t o Total dipole moment.

In above molecule, three A-B bonds are oriented at 120 ⁰ from one another. The resultant of any two bond moments is equal and opposite to the third. Therefore, resultant dipole moment is zero. Hence, molecule is non polar.