Answer:
CaO
Step-by-step explanation:
As lewis structure tells us about the charge on the ions in the lattice So by using it we can predict the balanced lattice of CaO And KF after proceeding we will find that CaO has the Ionic Bond of +2 and -2 which is greater than the ionic bond of KF which is +1 and -1 so greater the charge more the attraction and more the attraction more powerful bond becomes so after all of this we can say that Having higher bond strength leads to the much higher melting and boiling points.