Which of the following ionic compounds have the greatest lattice energy and hence highest melting/boiling point?1 pointNaFNaClMgOCaO

The lattice energy of an ionic compound is directly related to the charges on the ions and inversely related to the sizes of the ions. The greater the charge and the smaller the ion size, the greater the lattice energy.

Here are the charges and sizes of the ions in the given compounds:

• NaF: Na+ (charge +1, larger size) and F- (charge -1, smaller size)
• NaCl: Na+ (charge +1, larger size) and Cl- (charge -1, slightly larger size than F-)
• MgO: Mg2+ (charge +2, larger size) and O2- (charge -2, smaller size)
• CaO: Ca2+ (charge +2, larger size than Mg2+) and O2- (charge -2, smaller size)

Comparing these, MgO and CaO have ions with greater charges (+2 and -2) than NaF and NaCl (+1 and -1), so they will have greater lattice energies. Between MgO and CaO, Mg2+ is smaller than Ca2+, so MgO will have the greatest lattice energy.

Therefore, MgO has the greatest lattice energy and hence the highest melting/boiling point.