Chapter U2.43, Problem 1TAI

Interpretation Introduction

Interpretation: What makes a molecule polar is to be explained.

Concept Introduction:

There are two classes of molecules; polar and nonpolar. Polar molecules are attracted by a charged wand, where as a nonpolar molecule is not attracted by a charged wand. Examples of polar molecules are water, vinegar, and rubbing alcohol. Examples of nonpolar molecules are mineral oil, hexane, and motor oil.

Answer to Problem 1TAI

A polar molecule is a molecule that possesses partial charges on its atoms. There is a partial positive and partial negative charge on atoms. A molecule is polar due to the difference in electronegativity of atoms forming the bond which causes a difference in the sharing of electrons. One atom attracts the shared electrons more strongly than the other atom. Because of this displacement of electrons, one atom develops a partial negative charge and the other atom develops a partial positive charge. The result is a polar molecule.

Explanation of Solution

In a polar molecule, the bonded pair of electrons are not shared equally among the atoms. For example in HCl molecule, the hydrogen and chlorine atom do not share the bonded pair of electrons equally. The chlorine atom attracts the shared electrons more strongly than the hydrogen atom. This causes the shared electrons to be more close to the chlorine atom than the hydrogen atom. Because of this displacement of electrons, the chlorine atom develops a partial negative charge and the hydrogen atom develops a partial positive charge.

The tendency of an atom to attract shared electrons is called electronegativity. An atom with higher electronegativity attracts more electrons than an atom with low electronegativity. More electronegative atoms have partial negative charge and atoms that are less electronegative have a positive charge. This results in the formation of a polar bond.

Conclusion

A polar molecule is called a dipole as it has two poles; a positive end and a negative end.