May/June 2026 Paper 41

This question is about structure and bonding. Magnesium fluoride is an ionic compound. In Figure 3.1, complete the dot-and-cross diagrams to show the bonding in magnesium fluoride. The inner shells of electrons are shown. Show the charge on each ion.

Explain why magnesium fluoride has a high melting point.

Explain why magnesium fluoride conducts electricity when it is molten.

Fluorine, F${}_2$, consists of simple molecules. In Figure 3.2, complete the dot-and-cross diagram of a molecule of fluorine. Show outer shell electrons only.

The melting point and boiling point of fluorine are shown in Table 3.1.

Deduce the physical state of fluorine at $-240{}^{\circ }\mathrm{C}$. Use the data in Table 3.1 to explain your answer.