MgO has higher lattice enegy than NaF. Why?

Explanation

The lattice energy of an ionic compound increases with increase in charge on the ions and decrease with the sum of the ionic radiii. The charges on the two ions in `MgO` (`Mg^(2+)` and `O^(2-)` ions) is twice than that on the two ions in NaF (`Na^(+) and F^(-)` ions). the sum of ionic radii of `Mg^(2+) and O^(2-)` ion (0.64Å+1.40Å=2.04Å) is less than that of `Na^(+) and F^(-)` ions (0.95Å+1.36Å=2.31Å). therefore, MgO has a higher lattice energy than that of NaF.