Explain the following properties given suitable examples:
(i) Ferromagnetism;
(ii) Paramagnetism;
(iii) Ferrimagnetism.

3

(a)

Silver crystallizes in face-centred cubic unit cell. Each side of this unit cell has a length of 400 pm. Calculate the radius of the silver atom. (Assume the atoms just touch each other on the diagonal across the face of the unit cell. That is , each face atom is touching the four corner atoms.)

3

(a)

The well-known mineral fluorite is chemically calcium fluoride. It is known that in one unit cell of this mineral, there are 4 Ca²⁺ ions and 8 F^- ions and that Ca²⁺ ions are arranged in a fcc lattice. The F^- ions fill all tetrahedral holes in the face-centred cubic lattice of Ca²⁺ ions. The edge of the unitcell is 5.46\(\times \)10^-8 cm in length. The density of the solid is 3.18 g cm^-3. Use this information to calculate Avogadro's number. (Molar mass of CaF₂ = 78.08 G mol^-1)

3

(a)

Calculate the efficiency of packing in case of a metal crystal for
(a) simple cubic,
(b) body-centred cubic, and
(c) face-centred cubic (with the assumption that atoms are touching each other).

3

(a)

What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?

3

(a)

Classify the following as amorphous crystalline solids: Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

3

(a)

An ionic compound made up of atoms A and B has a face-centered cubic arrangement in the corner and atoms B are at the face-centers. If one of the atoms is missing from the corner, what is the simplest formula of the compound?

3

(a)

Calculate the approximate number of unit cells present in 1 g of gold. Given that gold crystallizes in the face-centred cubic lattice. (Atomic mass of gold=197u).

3

(a)

What is meant by anisotropy? Which of the two : quartz or glass shows this property?

3

(a)

Define the following terms:
(i) ferromagnetism
(ii) Ferrimagnetism

3

(a)

Define the following:
(i) Dislocation
(ii) F-centre
(iii) Anti-ferroelectric

3

(a)

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

3

(a)

What do you understand by non-stoichiometric compounds? Give examples.

3

(a)

The edge length of unit cell of a metal having molecular weight 75 g/mol is 5\(A^{ 0 }\) which crystallizes in cubic lattice If the density is 2g/cc then find the radius of metal atom.(N_A=6 x10²³ mol^-1 ) Give the answer in pm. 

3

(a)

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

3

(a)