Question

lattice energy of beo

Answer 1

BeO has less lattice energy than MgO ( because BeO is more covalent than MgO beacuse lattice energy is defined mainly for ionic compounds

Answer 2

lattice energies are higher for ions with multiple charges, 2+ and 2- ions will have larger energies than 1+ and 1- ions. Next smaller ions have larger lattice energies.  

LiCl is the only one with only singly charged ions, it will probably have the lowest lattice energy. Next is Na2S singly charge ion plus large S2- ion, then Na2O - O2- ion is smaller than S2- ion. MgO and BeO both have doubly charged ions, but Be2+ is smaller than Mg2+. Final order  

BeO > MgO > Na2O > Na2S > LiCl