Polar Molecules and Hydrogen Bonds

In the previous section, HCl was described as a polar molecule containing a polar covalent bond. The unequal sharing of electrons in a bond leads to what is referred to as a dipole. A dipole is symbolized using a modified arrow pointing toward the negative end of the dipole. For HCl, this can be represented as 

The dipole in HCl causes the H end of the molecule to possess a partial positive charge and the Cl end to possess a partial negative charge. This is denoted as 

The dipole created in HCl creates a polar molecule. The presence of polar covalent bonds does not necessarily mean the molecule will be polar. Some molecules contain two or more dipoles that cancel to give a nonpolar molecule. For example, in CO2 the two oxygens are attached to carbon by polar covalent bonds. 

The more electronegative oxygens attract the shared electrons that form the double covalent bonds. Thus, two polar double 

Percent Ionic Character Based on Difference in Electronegativity 

---

C) and this is the main reason for its ability to solubilize ionic solids, because the electrostatic attraction between anions and cations decreases 78.4 times in water. Polar liquids have much higher er values than non-polar molecules, and hydrogen-bonded liquids have exceptionally high values. It should be noted that e, is a macroscopic parameter derived for a continuous dielectric medium and cannot be used for interactions over molecular distances. 

---