Giant ionic structures
2 marks · NormalSodium chloride is an ionic compound with a giant lattice structure.
State TWO properties of sodium chloride that are linked to its giant ionic lattice, and briefly explain why the lattice causes each property.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
Also accept: high melting/boiling point (due to strong electrostatic forces in lattice); does not conduct electricity when solid (because ions are fixed); only conducts when molten/aqueous (because ions are free to move)
Common mistakes: Saying it conducts electricity when solid; Giving only one property
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States a correct property linked to ionic lattice structure (e.g. high melting point, electrical conductivity when molten/solution, brittle)
B2 (a) · 1 mark · Briefly links the property to the lattice structure (e.g. strong electrostatic forces, ions fixed/free to move)
Worked solution
One property: Sodium chloride has a high melting point.
Explanation: Because the giant lattice structure contains many strong electrostatic forces between ions, a lot of energy is needed to overcome them.
Another property: Sodium chloride only conducts electricity when molten or dissolved in water.
Explanation: In the solid lattice the ions are fixed in position, but when molten or in solution, the ions are free to move and carry charge.