Deriving the cooridinate numbers of both ions in rock salt

[rastamanrm]

How would I go about deriving the cooridinate numbers of both ions in rock salt, and,
how could I account for the differences in lattice enthalpy between the following;


LiCl (861 kJ/mole) - NaCl (787)
LiCl - LiF (1046)
LiCl - MgO (3850)

Cheers.

 

[Gokul43201]

rasta,

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[rastamanrm]

rasta,

We can not help until you first show us what effort you have made. Please read the posting guidelines (see "Rules" on top of page).

Well I do know that a coordinate number is the number of atoms surrounding an atom in a solid state lattice

And for the second bit, I assume LiCl would have a larger lattice energy due to the greater difference in electronegativity of both consituents, similar with the next one. Not sure about the last one.