In terms of band theory, what is the difference
(i) between a conductor and a semiconductor?
(ii) between a conductor and an insulator?

2

(a)

How are the following properties of crystals affected by Schottky and Frenkel defects?
(i) Density
(ii) Electrical conductivity.

2

(a)

Explain the following with suitable example:An n-type semiconductor.

2

(a)

Solids can be classified into three types on the basis of their electrical conductivities.
(i) Name three types of solids classified on the basis of electrical conductivities.
(ii) How will you explain such classification based theory?

2

(a)

The density of chromium metal is 7.2 g cm^-3 . If the unit cell is cubic with edge length of 289 pm, determine the type of unit cell (simple, body centred or face centred) [Atomic mass of Cr = 52 a.m.u., N₀ = 6.02 \(\times\) 10²³ mol^-1 ].

2

(a)

Cesium chloride crystallizes as cubic lattice and has a density of 4.0 g cm ^-3 . Calculate the length of the edge of the unit cell of cesium chloride. (Molar mass of CsCI = 168.5 b mol^-1).

2

(a)

A metal crystallises in a fcc structure. Atomic radius of the metal is 125 pm. Calculate the edge length of the unit cell of the metal.

2

(a)

Silver metal crystallizes with a face centered cubic lattice.The length of unit cell is found to be 4.077 x 10^-8 cm.Calculate atomic radius and density of silver. (Atomic mass of Ag = 108 u, NA = 6.02  x 10²³ mol^-1)

2

(a)

An element  with density 2.8 g cm^-3 forms a fcc unit cell with edge length 4 x 10^-8 cm Calculate the molar mass of the element (Given N_A = 6.022 x 10²³ mol^-1)

2

(a)

With the help of a labelled diagram show that there are four octahedral voids per unit cell in cubic close packed structure.

2

(a)

Calcium metal crystallize in a face-centred cubic lattice with edge length of 0.556nm.Calculate the density of the metal if contains (i)0.5% Frenkel defects(ii)0.2% Schottky defects.

2

(a)

You are given marbles of diameter 10mm.They are to be placed such that their centres are lying in a square bound by four lines each of length 40mm.What will be the arrangement of marbles in a plane so that maximum number of marbles can be placed inside the area?Sketch the diagram and derive an expression for the number of marbles per unit area.

2

(a)

Iron changes its crystal structure from body-centred to cubic close-packed structure when heated to 916⁰C.Calculate the ratio of the bcc crystal to that of ccp crystal,assuming that the metallic radius of the atom does not change.

2

(a)