Q. 6.84 - An Introduction to General, Organic, and Biological Chemistry

Question

The molecules ${\mathrm{CH}}_4$ and ${\mathrm{CH}}_3\mathrm{Cl}$ both have tetrahedral shapes. Why is ${\mathrm{CH}}_4$ nonpolar whereas ${\mathrm{CH}}_3\mathrm{Cl}$ is polar?

Step-by-Step Solution

Answer

${\mathrm{CH}}_4$ is nonpolar and ${\mathrm{CH}}_3\mathrm{Cl}$ is polar due to dipole moment.

Step 1 : Given information

We are given that both ${\mathrm{CH}}_4$ and ${\mathrm{CH}}_3\mathrm{Cl}$ have tetrahedral shape.

Step 2 : Simplify

In ${\mathrm{CH}}_4$ all of the atoms around the centre element (carbon) in a molecule of methane are equal (four hydrogens), and thus has a net dipole moment of $0$. (vectors of dipole moments cancel each other, dipole moment is zero). but There are various elements (one chlorine and three hydrogen atoms) surrounding the centre atom (carbon) in the chloromethane ${\mathrm{CH}}_3\mathrm{Cl}$ molecule, and thus has a greater net dipole moment. Therefore ${\mathrm{CH}}_4$ is nonpolar whereas ${\mathrm{CH}}_3\mathrm{Cl}$ is polar.