Chemistry

Problem

MgO melts at a temperature more than 1500 °C higher than that of NaCl. Which statement best accounts for this difference? a) Because the

\mathrm{Mg^{2+}}

ion is considerably smaller than

\mathrm{Na^{+}}

, the ions in MgO are packed more closely together, giving stronger ionic attractions that require a higher melting temperature. b) The

\mathrm{Mg^{2+}}

and

\mathrm{O^{2-}}

ions in MgO carry twice the charge of the ions in NaCl, producing much stronger Coulombic attractions that require more energy to break. c) MgO forms a three-dimensional covalent network, whereas NaCl is held together only by ionic attractions. d) Because MgO has a greater molar mass than NaCl, its London dispersion forces are significantly stronger.

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