The four bonds of carbon tetrachloride (CCl4) are polar, but the molecule is nonpolar because the bond polarity is canceled by the symmetric tetrahedral shape. When other atoms substitute for some of the Cl atoms, the symmetry is broken and the molecule becomes polar. Rank the following molecules from the least polar to the most polar: CH2Br2, CF2Cl2, CH2F2, CH2Cl2, CBr4, CF2Br2.