To determine whether the molecules of the compounds are polar or nonpolar, we need to look at their molecular geometry and the electronegativity of the atoms involved.
- HF (Hydrogen Fluoride): This molecule is polar. Fluorine is much more electronegative than hydrogen, causing the electrons to be drawn more towards the fluorine atom. This results in a dipole moment with a partial negative charge (δ-) on the fluorine and a partial positive charge (δ+) on the hydrogen.
- CS2 (Carbon Disulfide): This molecule is nonpolar. Both sulfur atoms have similar electronegativities, and the linear shape of the molecule means that any dipoles created by the C-S bonds cancel each other out.
- CH4 (Methane): This molecule is nonpolar. Although there are polar C-H bonds, the symmetrical tetrahedral shape allows the dipole moments to cancel each other, resulting in a molecule that is overall nonpolar.
- NCl3 (Nitrogen Trichloride): This molecule is polar. Nitrogen is less electronegative than chlorine, creating a dipole moment where the nitrogen has a partial positive charge and the chlorine atoms have partial negative charges. The trigonal pyramidal shape of the molecule prevents the dipoles from canceling out.
In summary, HF is polar, CS2 and CH4 are nonpolar, and NCl3 is polar.