Which pair of compounds is listed in order of increasing (more exothermic) lattice energy?

Which pair of compounds is listed in order of increasing (more exothermic) lattice energy?

LiF < LiI   
NaCl < KCl    
MgO < CsCl    
CaO < BaCl2
LiF < MgO

Answer

Answer : LiF < MgO Explanation Lattice energy depends on the charge of the constituent ions. In MgO, the charge of cation and anion are +2 and -2 respectively.In LiF, the charge of cation and anion are +1 and -1. Similarly, if the electronegativity of the anion is higher, the higher will be the lattice energy. Also, an ionic compound with smaller cation size will have higher lattice energy. Here, the correct order is, LiF > LiI NaCl > KCl    MgO > CsCl   CaO > BaCl2

LiF < MgO

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