Polarity

These bonds involve the sharing of electrons between atoms. However, the sharing might not always be equal.

Electronegativity: This is an atom's tendency to attract electrons towards itself in a bond.
Polar Covalent Bond: When two atoms have a significant difference in electronegativity, the electrons in the bond are pulled closer to the more electronegative atom. This creates a partial negative charge (δ-) on the electronegative atom and a partial positive charge (δ+) on the less electronegative atom. This unequal sharing results in a polar covalent bond.

Molecular Polarity: The Big Picture

The polarity of a molecule depends not only on the polarity of its bonds but also on its overall shape.

Dipole Moment: This is a measure of the polarity of a molecule. It considers both the magnitude of the partial charges and the distance between them. A molecule with a net dipole moment (unequal distribution of positive and negative charges) is considered polar.
Molecular Shape: The arrangement of atoms in a molecule plays a role. Even if a molecule has polar bonds, if the geometry cancels out the individual bond polarities, the overall molecule might be nonpolar. (e.g., CO2)

Impacts of Polarity:

Polarity has a significant influence on various aspects of a molecule's behavior:

Intermolecular Forces: Polar molecules can attract each other through electrostatic interactions (dipole-dipole interactions, hydrogen bonding). This can influence properties like boiling point, melting point, and viscosity.
Solubility: Polar molecules tend to dissolve well in other polar solvents (like water) because they can form favorable interactions with the solvent molecules. This is the principle behind "like dissolves like."
Chemical Reactions: Polarity can influence the reactivity of molecules. Polar molecules can participate in reactions involving ionic compounds or other polar molecules more readily than nonpolar molecules.

Tips for Studying Polarity:

Understand the concept of electronegativity and how it affects bond polarity.
Learn to predict the polarity of molecules based on their Lewis structures and molecular shapes (VSEPR theory).
Recognize the connection between polarity and intermolecular forces, solubility, and chemical reactions.
Practice identifying polar and nonpolar molecules given their structures.