Why do ionic compounds have higher melting and boiling points despite having smaller radii?

Why do ionic compounds have higher melting and boiling points despite having smaller radii?


I thought that the closer the two ions are, the larger the repulsive force, and therefore it should rather require less energy to separate them (and at further distances apart, a lower melting point is observed because there is less attraction).


This is not a question of ionic compounds *vs.* covalent compounds, which is covered in [this question](https://chemistry.stackexchange.com/questions/5394/why-is-the-melting-boiling-point-of-ionic-bond-higher-than-covalent-bond). To be clear, I am interested in the comparison of ionic compounds with ionic compounds.




As pointed out in a comment, there is a problem with your second sentence: 



> 
> "I thought that the closer the two ions are, the larger the repulsive force, and therefore it should rather require less energy to separate them..." 
> 
> 
> 


This statement is technically correct, in that the *repulsive* forces between the two atoms do increase with decreasing bond length. And it is true that two atoms having a charge of the same polarity would exhibit increasing repulsion as the distance between them decreases.


However, in the case of the oppositely charged atoms found in ionic bonds, the *attractive* electrostatic forces also increase with decreasing bond length, which is the reason for the strong bonding and thus high melting points of ionic compounds. 


A discussion of the bond strength of ionic compounds is given in [this Wikipedia article](https://en.wikipedia.org/wiki/Ionic_bonding#Bond_strength), which summarizes that the ionic bond strength can be determined as the sum of the attractive electrostatic energy and short-range repulsive energy. 


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