Fig. 1 shows part of the crystal structure formed when sodium reacts with chlorine to make sodium chloride for winter road salt. The large circles represent...
Question 1 Report
Fig. 1 shows part of the crystal structure formed when sodium reacts with chlorine to make sodium chloride for winter road salt. The large circles represent chloride ions and the smaller circles represent sodium ions. A student notes that the solid is hard but does not conduct electricity until it is melted.
(a) Give the name of the type of bond between a sodium ion and a chloride ion. [1]
(b) Describe how a sodium atom becomes a sodium ion. [2]
(c) Use the structure in Fig. 1 to give one reason why solid sodium chloride does not conduct electricity. [1]
(d) Describe why molten sodium chloride can conduct electricity. [2]
Answer Details
(a) The bond between sodium and chloride ions is an ionic bond [1]. It is the electrostatic attraction between oppositely charged ions.
(b) A sodium atom loses one electron [1], forming a positive sodium ion, Na+ [1].
(c) In solid sodium chloride, ions are held in fixed positions and cannot move through the lattice [1]. Therefore there are no mobile charged particles to carry current.
(d) When sodium chloride melts, its ions become free to move [1]. These moving charged ions carry electrical charge, so the liquid conducts [1].
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