Just as individual bonds in a molecule are often polar, moleculesas a whole are also often polar because of the netsum of individual bond polarities. There are three possiblestructures for substances with the formula C2H2Cl2, two ofwhich are polar overall and one of which is not.(b) Which of the three structures is nonpolar, and whichtwo are polar? Explain.

Molecular polarity refers to the distribution of electrical charge across a molecule, which determines whether it has a positive or negative end. This is influenced by the presence of polar bonds and the molecular geometry. A molecule is polar if it has a net dipole moment, meaning the vector sum of all bond dipoles does not cancel out.

Bond polarity arises from the difference in electronegativity between two atoms in a bond. When one atom is more electronegative, it attracts the shared electrons more strongly, creating a dipole moment. In C2H2Cl2, the C-Cl bonds are polar due to chlorine's higher electronegativity compared to carbon, affecting the overall polarity of the molecule.

Molecular geometry describes the three-dimensional arrangement of atoms in a molecule. The shape of a molecule, determined by the VSEPR theory, influences how bond dipoles add up. For C2H2Cl2, different arrangements of chlorine and hydrogen atoms lead to distinct geometries, which can result in either a polar or nonpolar molecule depending on the symmetry of the structure.