1.(a) MgO has the rock-salt structure. The MgO crystal has a value of 0.514 for the radius ratio. The length of a side of the unit cell for MgO is 4.24 Å.
(i) Draw the structure of this molecule.
(ii) Determine the radii of Mg 2+and O2-, assuming that the O 2-ions are in contact with one another.
(b) Define what is meant by the “coordination number” of a crystal structure.
(c) Determine the coordination number for each of the following crystal structures:
(i) Face-centred cubic (NaCl)
(ii) Body-centred cubic (CsCl)
(iii) Zinc blende (ZnS)
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