---
title: "A student investigates the thermal properties of refractory ceramic materials and records the data in the table below.  | Compound | Cation | Anion | Interionic distance (\\(\\text{pm}\\)) | Melting point (\\(^\\circ\\text{C}\\)) | | :— | :— | :— | :— | :— | | \\(\\text{MgO}\\) | \\(\\text{Mg}^{2+}\\) | \\(\\text{O}^{2-}\\) | \\(212\\) | \\(2852\\) | | \\(\\text{NaF}\\) | \\(\\text{Na}^+\\) | \\(\\text{F}^-\\) | \\(231\\) | \\(993\\) |  Both \\(\\text{MgO}\\) and \\(\\text{NaF}\\) crystallize in the same cubic lattice geometry, and each ion in both compounds is isoelectronic with neon (\\(10\\) electrons). Which of the following statements best accounts for the significantly higher melting point of \\(\\text{MgO}\\) compared to \\(\\text{NaF}\\)?"
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url: "https://nerd-notes.com/ubq/120183/"
date_modified: "2026-08-21T16:02:51+00:00"
---

# A student investigates the thermal properties of refractory ceramic materials and records the data in the table below.

| Compound | Cation | Anion | Interionic distance (\(\text{pm}\)) | Melting point (\(^\circ\text{C}\)) |
| :— | :— | :— | :— | :— |
| \(\text{MgO}\) | \(\text{Mg}^{2+}\) | \(\text{O}^{2-}\) | \(212\) | \(2852\) |
| \(\text{NaF}\) | \(\text{Na}^+\) | \(\text{F}^-\) | \(231\) | \(993\) |

Both \(\text{MgO}\) and \(\text{NaF}\) crystallize in the same cubic lattice geometry, and each ion in both compounds is isoelectronic with neon (\(10\) electrons). Which of the following statements best accounts for the significantly higher melting point of \(\text{MgO}\) compared to \(\text{NaF}\)?

A student investigates the thermal properties of refractory ceramic materials and records the data in the table below.

| Compound | Cation | Anion | Interionic distance (\(\text{pm}\)) | Melting point (\(^\circ\text{C}\)) |
| :--- | :--- | :--- | :--- | :--- |
| \(\text{MgO}\) | \(\text{Mg}^{2+}\) | \(\text{O}^{2-}\) | \(212\) | \(2852\) |
| \(\text{NaF}\) | \(\text{Na}^+\) | \(\text{F}^-\) | \(231\) | \(993\) |

Both \(\text{MgO}\) and \(\text{NaF}\) crystallize in the same cubic lattice geometry, and each ion in both compounds is isoelectronic with neon (\(10\) electrons). Which of the following statements best accounts for the significantly higher melting point of \(\text{MgO}\) compared to \(\text{NaF}\)?

- **A.** \(\text{MgO}\) has a higher melting point because the magnitude of the product of the ionic charges in \(\text{MgO}\) (\(\left|(+2)(-2)\right| = 4\)) is four times greater than that in \(\text{NaF}\) (\(\left|(+1)(-1)\right| = 1\)), resulting in substantially stronger Coulombic attractions within the crystal lattice.
- **B.** \(\text{MgO}\) has a higher melting point because the electronegativity difference between \(\text{Mg}\) and \(\text{O}\) is greater than that between \(\text{Na}\) and \(\text{F}\), creating individual ionic bonds with greater covalent bond character and higher bond energies.
- **C.** \(\text{MgO}\) has a higher melting point because \(\text{Mg}^{2+}\) has a higher nuclear charge than \(\text{Na}^+\), allowing the magnesium cations to form a rigid three-dimensional network of shared electron pairs with oxygen.
- **D.** \(\text{MgO}\) has a higher melting point because \(\text{MgO}\) formula units have a greater dipole moment than \(\text{NaF}\), producing stronger intermolecular dipole-dipole attractions and London dispersion forces.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120183/*