Question

Which of the following statements best explains the difference in melting point between $MgO\left({2852}^{\circ }C\right)$ and $NaF\left({1819}^{\circ }C\right)$?

• A. Sodium, being an alkali metal, is more reactive magnesium, an alkaline earth metal.
• B. Magnesium and oxygen have higher charge values and therefore have greater Coulombic attractions.
• C. Fluorine is more electronegative than oxygen.
• D. The oxide ion is larger than the fluoride ion.

Answer 1

Answer: (B)

Magnesium and oxygen have higher charge values and therefore have greater Coulombic attractions.

Coulumbic attraction between $2$ ions$=\frac{k{q}_1{q}_2}{r^2}$ i.e., directly proportional to charge. ${Mg}^{2+}$ and $O^{2-}$ have higher charge values hence have greater attraction force hence have higher melting point. Thus correct option is B.