Which Solid Has the Highest Melting Point?

[geffman1]

Homework Statement

hey guys, just wondering if you could tell me which of these is polar and how to do it thanks? the question is asking for the highest melting point, so i believe it relates to which is polar. any help would be greatly appreciated.

Homework Equations

Which of the following solids would have the highest melting point?
NaI
CsF
MgO
MgCl2
KF

The Attempt at a Solution

 

[Borek]

It is all about Coulomb forces.