Question

the melting and boiling points of ionic compounds are very high why?

Answer 1

In ionic compounds, the constituent particles are the ions. As a result, these are held together by the strong ionic bonds and the principle forces are the electrostatic forces that hold the ions together in a crystal lattice. Breaking the crystal lattice means pulling the negative and the positive ions apart, which requires a lot of energy as the electrostatic forces are very strong. Hence the melting and the boiling point of ionic compounds are very high.