3. explain and show why ch₃f is a polar molecule, while cf₄ is not.

Explanation:

Step1: Analyze electronegativity

Electronegativity of F > C > H. In $CH_3F$, C - F bond is polar due to electronegativity difference.

Step2: Examine molecular geometry

$CH_3F$ has a tetrahedral geometry with a lone - pair of electrons (not shown in simple formula) around C. The polar C - F bond creates a net dipole moment, making it polar.

Step3: Analyze $CF_4$ geometry

$CF_4$ also has a tetrahedral geometry. But the four C - F bonds are symmetrically arranged. The bond dipoles cancel each other out, resulting in no net dipole moment, so it is non - polar.

Answer:

$CH_3F$ is polar because of the polar C - F bond and non - symmetric molecular geometry creating a net dipole moment. $CF_4$ is non - polar as the symmetric arrangement of four C - F bonds causes the bond dipoles to cancel out.