Magnitude of Electric Force Between Two Ions

[tylerc1991]

Homework Statement

Find the magnitude of the electric force between a Na+ ion and a Cl- ion separated by .5 nm.

Homework Equations

|F| = (kQq)/r^2

The Attempt at a Solution

So the problem I am having with this question is this: my first attempt at a solution was to designate |Q| = |q| = 1.6 * 10^-19 C. After which I can just plug these into the equation. But after visiting my professor he told me to multiply Q by 10 (because there are 10 electrons in the Na+ ion) and likewise to multiply q by 18 (because Cl- has 18 electrons). This makes very little sense to me and I hope that someone can help me with this problem. By the way, the answer I originally obtained was 9.23 * 10^-10 N.

 

[0ddbio]

I think what your professor told you is incorrect.
A Na atom for example is neutral, it may have 11 electrons but it also has 11 protons.
Your Na+ ion has 10 electrons yes, but it also has 11 protons.

The only thing I can think of is maybe he wants you to do all the charges, so putting in 10 electrons and also 11 protons for Na+. Which of course is the same as just treating it as a single +e charge.