Chapter 9 - Section 9.4 - Ionic Bonding: Lewis Symbols and Lattice Energies - For Practice - Page 392: 9.2

order is $LiBr $ < $KI$ < $CaO$

$LiBr $ and $KI$ have low lattice energy because magnitude of charge on ions is 1. $CaO$ has higher lattice energy because magnitude of charge on ions is 2. Among $LiBr $ and $KI$, $LiBr $ has lower lattice energy due to large size of $Br$ compared to $Li$. So, order is $LiBr $ < $KI$ < $CaO$