Suppose you have a crystal composed of elements X and Y in which the radius ratio is approximately ½, so that the sodium chlorid
e lattice is possible. Each ion is about the same size as Na+ and Cl-, respectively, but each ion is doubly charged X++ and Y--. Would XY (s) have a higher or lower melting point than NaCl (s)?
The electrostatic force (F) between ions in an ionic lattice can be estimated using Coulomb's Law.
where,
k is the Coulomb's constant
q₁ and q₂ are the charges of the ions
r is the distance between the ions
X⁺⁺ and Y⁻⁻ are doubly charged with respect to Na⁺ and Cl⁻ so the force between them is 4 times the force between Na⁺ and Cl⁻. Since the force is stronger, it would require more energy to break it to take it to the liquid state, so a higher melting point is expected.
Heat energy because the energy in seismic waves that causes the ground to shake is heat energy. Heat energy associated with friction on the fault slip surface
