Predict the structure of MgO crystal and coordination number of its cation in which cation and anion radii are equal to 65 pm and 140 pm respectively.

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Calculate the approximate numbert of unit cells present in 1 g of ideal NaCl crystals.

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What are ferromagnets and ferro-electrics? Give on example of each case.

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What are point defects in crystals and how do they develop?

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Ionic solids which have anionic vacancies to metal excess defect develop colour. Explain with the help of a suitable example.

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Copper has fcc structure. If its densities 8.92 g cm^-3 . Calculate its radius if atomic mass of Cu is 63.5 g mol^-1

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Compounds having general molecular formula  \(AFe_{ 2 }O_{ 4 }\) are called ferrites and posses spinel type structures. Some common examples are \(MgFe_{ 2 }O_{ 4 }\)  and \(ZnFe_{ 2 }O_{ 4 }\) They may be thought of being formed by replacing \(Fe^{ 2+ }\) ions present in \(Fe_{ 3 }O_{ 4 }\) by bivalent cations such as \(Mg^{ 2+ },Zn^{ 2+ }\) ions etc. Now answer the following questions :
(i) What types of materials are ferrites?
(ii) What are the main uses of ferrites?

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