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)

hi,

the answer is d.indefinite shape but definite volume, let go oogle u out

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it would be d. henry moseley

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and sorry if i'm late. have a good rest of your day! : d

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).