The polarity of a molecule can be assessed by analyzing both its molecular geometry and the electronegativity of its constituent atoms.

To grasp the concept of polarity, it is essential to define what it entails. Polarity refers to the uneven distribution of electric charges within a molecule, resulting in the formation of a positive end and a negative end. This uneven charge distribution arises from variations in electronegativity among the atoms within the molecule. Electronegativity quantifies an atom’s ability to attract a bonding pair of electrons. When two atoms in a molecule possess differing electronegativities, the bonding electrons are drawn more closely to the atom with the higher electronegativity, leading to the creation of a dipole moment, which signifies a separation of electrical charges.

The molecular geometry, or the spatial arrangement of atoms in a molecule, also significantly influences its polarity. A symmetrical molecule tends to be nonpolar, even if it contains polar bonds. This is because in symmetrical molecules, the dipole moments cancel each other out, resulting in an overall nonpolar character. For instance, carbon dioxide ($\text{CO}_2$) is a linear molecule with two polar $\text{C=O}$ bonds; however, it is nonpolar because the dipole moments of these two bonds negate each other.

Conversely, an asymmetrical molecule is likely to be polar. In such molecules, the dipole moments do not cancel out, leading to an overall polar characteristic. A prime example is water ($\text{H}_2\text{O}$), which has a bent molecular geometry and features two polar $\text{O-H}$ bonds. The dipole moments of these bonds do not cancel, rendering the molecule polar.

In summary, to determine a molecule’s polarity based on its structure, one must consider both the electronegativities of its atoms and its molecular geometry. If the molecule consists of atoms with varying electronegativities and exhibits asymmetry, it is likely to be polar. In contrast, if the molecule is symmetrical, it is likely to be nonpolar, even if it contains atoms with different electronegativities.