(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The ionisation energy of Li is 5.39eV and the electron affinity of F is 3.40eV. Give a lower bound for the modulus of the crystallisation energy of Li+F-

2. Relevant equations

Not entirely sure of the equation to use, but have this one in my notes:

U = - (q1q2/r(1,2)) . alpha . (1 / 4Pi E)

where E is the permeability of free space (I believe)

3. The attempt at a solution

I haven't really attempted this to any meaningful degree, the problem is that I don't know how I can work this out when I'm not given a value for r (presumably the radius between atoms or ions??) nor am I sure what values I'm supposed to use for the charges q1 and q2.

I don't expect anyone to solve this for me, but if you could clarify what you think I need to do to work this out I'd be greatful. My lecturer is great on giving derivations and formulas, but never seems to explain things very well.

Cheers

Kel

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# Homework Help: Solid state - crystallisation energy

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