which halides of Li,Be and Mg are covalent and which are ionic???

as the size of the cation decrease covalent nature increase

ie,

as lithium being small in size ,it would be having most covalent character

then comes beryllium 

and the least covalent character is for halides of magnesium

the least covalent is most ionic 

as the metallic character increases ie, as the size icreases the ionic nature increases 

so the most ionic is halides of magnesium

and least ionic is halide of lithium 

hope u got ur answer