By Arthur Ramsay
Updated Aug 30, 2022

Polarity in chemistry describes how unevenly electrons are shared between atoms in a bond. When electrons spend more time closer to one atom, that atom becomes partially negative while the other becomes partially positive, creating a dipole. This principle underpins many everyday phenomena—from the solvent properties of water to the behavior of biomolecules. According to research from the University of Arizona, water has a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms.

Step 1: Draw the Lewis Structure

Begin by sketching the Lewis structure of your molecule. Identify every element present, as the geometry of the molecule will influence how dipoles add up.

Step 2: Look Up Electronegativity

Consult a reliable electronegativity table to find the electronegativity value for each element in the molecule.

Step 3: Calculate Electronegativity Differences

Subtract the electronegativity of one atom in a bond from that of the other and take the absolute value. Use the following thresholds:

• 0.0 – 1.2: nonpolar bond
• 1.2 – 1.8: polar covalent bond
• ≥1.8: ionic bond

Step 4: Repeat for Every Bond

Apply the calculation to each bond in the molecule to determine its individual polarity.

Step 5: Visualize Dipole Directions

Place an arrow on each polar bond, pointing toward the more electronegative atom. If all arrows converge toward a single center, the dipoles cancel and the molecule is overall nonpolar. If the arrows do not cancel, the molecule possesses a net dipole moment and is polar.

Warning

Electronegativity values can shift depending on the chemical environment—elements such as fluorine may display different values when bonded to different partners. Always consider the specific bonding context when applying these rules.