plot ...plot ...plot ...please
 

can u help me on this please ...???!!! :(

Make an accurate plot of FA versus r for an Mg2+ - O2- pair. Conceder the range of r from 0.2 to 0.7 nm.

What is FA?

It could be nothing at all ;)
but then again it could be the force of attraction

Oh, I see. You'll need Coulomb's Law then.

http://en.wikipedia.org/wiki/Coulomb%27s_law

q1 and q2 are the absolute values of the charges of the ions - in both cases, 2 fundamental units (with one fundamental unit being 1.602 × 10^−19 coulomb). This will give you an equation of the form of

F = c/r

with c being a constant equal to kq1q2.

This sort of graph should look something like the first one on this page:

http://id.mind.net/~zona/mmts/functi.../oneOverX.html

F would be the vertical, or y, axis, while r would be the horizontal axis. Of course r goes from one positive value to another so you will only show part of the positive part of the graph.