What is the SI unit of electric dipole moment and its magnitude range?

SI Unit:
The official SI (Système International) unit for the electric dipole moment is the coulomb-meter (C·m).

• Derivation: This unit comes directly from the formula p = q × d, where charge (q) is measured in coulombs (C) and distance (d) is measured in meters (m).

Common Unit and Magnitude Range:
The coulomb-meter is a very large unit for practical use at the molecular level. Therefore, a much more common non-SI unit used in physics and chemistry is the Debye (D), named after physicist Peter Debye.

• Conversion: 1 Debye (D) = 3.336 × 10^-30 C·m
• Magnitude Range:
  • Non-polar Molecules: Symmetrical molecules like N₂, O₂, CO₂, and CH₄ have a net dipole moment of 0 D.
  • Slightly Polar Molecules: Molecules with low electronegativity differences, like C-H bonds, have very small dipoles (e.g., toluene ≈ 0.36 D).
  • Common Polar Molecules: Molecules like HCl (≈ 1.1 D), NH₃ (≈ 1.47 D), and H₂O (≈ 1.85 D) have moderate dipole moments.
  • Highly Polar/Ionic: Species with large charge separations, like gaseous KBr, can have very high dipole moments (≈ 10.5 D).

In summary, for most common molecules, the magnitude ranges from 0 D (non-polar) to around 2 D (highly polar).