How many of the following are covalent in nature.  $LiI,LiBr,LiCl,NaCl$
 

Lithium-ion has a small size. Hence it can easily distort the electron cloud of the anion. Hence lithium halides have partial covalent character. 

The anion with a larger size can be easily distorted. The increasing order of the ionic size is Cl⁻<Br⁻<I⁻. Hence among the given halides, lithium chloride is least covalent in nature and lithium iodide is most covalent in nature.