Answer:
The correct answer is C.
Explanation:
The compound with the highest melting point according to the ion bond model is the one with the greatest electronegativity difference, since the ion bond is stronger and therefore more difficult to break.
The electronegativity difference is calculated as the electronegativity difference of the atoms of the molecule.
AlN: Al (1,61) and N (3,04) so the difference gives 1,43.
MgO: Mg (1,31) and O (3,44) so the difference gives 2,13.
NaF: Na (0,93) and F (3,98) so the difference gives 3,05.
CaS: Ca (1) and S (2,58) so the difference is 1,58.
RbI: Rb (0.82) and I (2.66) so the difference is 1.84.
Analyzing the different cases, we can conclude that the molecule that presents the greatest difference in electronegativity is NaF, so it will have a higher boiling point due to the attraction force between its atoms.
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