What is the binding energy in NaCl?

[pearapple]

Homework Statement

Each Na atom transfers 1/6 of an electron, on average, to each Cl atom. Estimate the binidng energy of the ionic bonds in NaCl.

Homework Equations

The Attempt at a Solution

The answer says to use k*q1*q2 / r, where k is the electric constant, q1 and q2 are the charges, and r is the separation between the charges.

So it gives k*(1/6)e*e / r.

I'm wondering what would happen if it were a different atom. In NaCl, Na has a charge of +1 and Cl has a charge of -1. If I wanted to calculate the binding energy of something with charges that weren't necessarily 1, how would this change?

 

[Borek]

This is based on a simple coulomb interactions between point charges.

 

[pearapple]

I know. It's the charges of the ions I'm unclear on. I just wanted to know what the answer would look like if the question was about, say MgO instead of NaCl.

 

[Borek]

MgO would mean charges +2 and -2. 1/6th is just effect of the geometry, so in the case of MgO I would expect 2/6th.