Question 1013508
Coulomb's law states that 
{{{F = kq[1]q[2]/d^2}}}
We are solving for the distance d in this case...so
2.0 x 10^-12 N = (8.99 x 10^9)(4.0 x 10^-14 C)^2 / d^2
gives us
d = .00268 m = 2.68 mm