Here's why:
* Electronegativity: Chlorine is more electronegative than carbon. This means that chlorine has a stronger attraction for electrons in the C-Cl bond.
* Polar Bond: The unequal sharing of electrons in the C-Cl bond creates a partial negative charge (δ-) on the chlorine atom and a partial positive charge (δ+) on the carbon atom. This creates a dipole moment in the molecule.
* Molecular Geometry: Chloromethane has a tetrahedral shape, with the chlorine atom positioned asymmetrically. This shape, combined with the dipole moment, results in a net dipole moment for the entire molecule.
In contrast, methane has only carbon-hydrogen bonds. Hydrogen and carbon have similar electronegativity values, so the C-H bonds are essentially nonpolar. Since there are no significant polar bonds, methane has no overall dipole moment and is a nonpolar molecule.
In summary: Chloromethane has a polar C-Cl bond and a net dipole moment due to its molecular geometry, making it a polar molecule. Methane has no significant polar bonds and no net dipole moment, making it a nonpolar molecule.
