The magnitude of electrostatic force between two tiny spherical balls carrying charges $$q_1$$ and $$q_2$$ separated by distance $$r$$ in free space is given by $$F=K\frac{q_1q_2}{r^2}$$ where $$K=9\times10^9$$ in SI units. Two tiny spherical balls of carbon-$$C_{12}^{6}$$ weighing $$1\,\mathrm{g}$$ each are kept $$1\,\mathrm{cm}$$ apart in free space.The two
spheres carry equal and opposite charges. The magnitude of electrostatic force of attraction between the
two charged spheres is F = $$1.0\times10^{-5}\,\mathrm{N}$$. The ratio of the number of excess electrons to total number of
atoms in the negatively charged sphere is