Question

What is the electric field at a distance of 0.9 nm from a carbon nucleus containing 6 protons and 6 neutrons

Answer 1

How about E = K 6 e/r^2 ?

with e the elementary electronic charge (here +ve) and

r = 0.9 x 10^-9m

and K = 9 x 10^9.

Much harder: trying to position the charges and finding individual fields then adding.