What characteristic of magnesium oxide leads to a higher melting point compared to sodium chloride?

Magnesium oxide has a higher melting point than sodium chloride primarily due to the higher charge on the ions. In magnesium oxide, each magnesium ion (Mg²⁺) carries a +2 charge, while each oxide ion (O²⁻) also carries a -2 charge. This results in a strong electrostatic attraction between the positively and negatively charged ions, leading to a more stable ionic lattice structure with greater ion-ion interactions.

In contrast, sodium chloride consists of sodium ions (Na⁺) with a +1 charge and chloride ions (Cl⁻) with a -1 charge. The resultant ionic interactions are therefore weaker than those seen in magnesium oxide. The greater the charge of the ions, the stronger the electrostatic forces of attraction between them, which significantly contributes to the higher melting point of magnesium oxide compared to sodium chloride.

The other characteristics, such as metallic bonds, the size of the ionic radii, or the number of ions in the lattice structure, do not primarily determine the melting point in this comparison. The key factor here is the ion charge, which directly influences the strength of the ionic bond, leading to differences in melting points.