Topic 4 Extension questions 1Describe the bonding in giant metallic, giant ionic and giant covalent structures so as to show that all three structures rely on electrostatic attractions to provide the forces which hold atoms or ions together.

2Explain why the enthalpy change of atomisation of bromine is equal to half the sum of its enthalpy change of vaporisation and its bond enthalpy.

3a)Use the values of various quantities in Figures 4.20 and 4.21 in the Students Book and (H

b)Using your BornHaber cycle, calculate the lattice energy of sodium chloride.

c)Which enthalpy term plays the greatest part in determining the stability of sodium chloride?4a)How would you estimate the lattice energy of the hypothetical compound, NaCl2?

b)Assuming that the lattice energy of NaCl2 is (2017kJmol1 and the second ionisation energy of sodium is +4563kJmol1, draw up a BornHaber cycle to calculate a value for the enthalpy change of formation of NaCl2. (The values of other quantities required for the calculation can be obtained from Figures 4.20 and 4.21 in the Students Book.)

c)Comment on the stability of NaCl2 with respect to the elements sodium and chlorine and with respect to the compound NaCl.5a) Draw dot-and-cross diagrams to show the outer shell electrons in

i)ammonia, NH3

ii)gaseous aluminium chloride which forms simple molecules with the molecular formula AlCl3.

b)Explain how dative covalent bonding between ammonia and gaseous aluminium chloride results in a solid compound of formula AlCl3.NH3.

c)At room temperature, gaseous aluminium chloride dimerises, as a result of dative covalent bonds, to form a white solid, Al2Cl6.

Draw a dot-and-cross diagram to show the bonding in Al2Cl6.

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G. Hill and A. Hunt 2008 Edexcel Chemistry for AS CD-ROM