Chapter 18, Problem 17RQ

How can a molecule be nonpolar when it consists of atoms that have different electronegativities?

To determine

The reason as to why molecule consists of atoms having different electronegativity are non-polar in nature.

Answer to Problem 17RQ

When the dipole moment cancels out each other in a molecule it is considered as a nonpolar molecule even though they have different electronegativities.

Explanation of Solution

A covalent bond is a type of bond where atoms are held together by the mutual attraction of a shared pair of electrons. The atoms of the same elements or the atoms of elements having very less electronegativity difference tend to share the electrons mutually for the covalent bond formation.

The mutual sharing of electrons between the atoms of a slight electronegativity difference creates a dipole. The dipole is a charge separation of a molecule where the atoms with slight higher electronegativity tend to attract electrons more towards it and gain a partial negative charge while the other element presents with slightly lesser electronegativity gains a partial positive charge.

When the ions in a molecule are of different electronegativities and due to geometry pulls each other in the opposite direction, this effectively cancels the dipole moment of each other. Thus, results in a nonpolar molecule as a whole.

Conclusion:

Therefore, in a molecule having different values of electronegativity if the dipole moment cancels out each other it is a nonpolar molecule.