* Lewis structure: H-C-H

* VSEPR shape: tetrahedral

* Polarity: nonpolar

CH₃Cl

* Lewis structure: H-C-Cl

* VSEPR shape: tetrahedral

* Polarity: polar

Explanation:

In CH₄, the four hydrogen atoms are arranged symmetrically around the carbon atom. This means that the electronegativity of the hydrogen atoms cancels out, and the molecule is nonpolar.

In CH₃Cl, the chlorine atom is more electronegative than the hydrogen atoms. This means that the electrons in the C-Cl bond are pulled towards the chlorine atom, creating a polar bond. The molecule as a whole is also polar, because the positive end of the C-Cl bond is closer to the chlorine atom than the negative end.