From Coulomb’s law $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ F = \frac{1}{4\pi\varepsilon_{0}}\frac{q_{1}q_{2}}{r^{2}}$ Or $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \varepsilon_{0} = \frac{q_{1}q_{2}}{4\pi Fr^{2}}$ $\therefore Units\ of\ \varepsilon_{0}\ (permittivity)$ $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{C^{2}}{N - m^{2}} = C^{2}N^{- 1}m^{- 2}$