In an f.c.c. unit cell, atoms are numbered as shown below. The atoms not touching each other are (Atom numbered 3 is face centre of front face).

(A) 3 & 4                                               

(B) 1 & 3 

(C) 1 & 2                                               

(D) 2 & 4

A metal crystallizes in two cubic phases, face centred cubic (fcc) and body centred cubic (bcc) whose unit cell length are 3.5 and 3.0 Å respectively. Calculate the ratio of density of fcc and bcc. 

(A) 2.123                                     

 (B) 1.259

(C) 5.124                                       

(D) 3.134

A compound alloy of gold and copper crystallizes in a cube lattice in which the gold atoms occupy the lattice points at the corners of a cube and the copper atoms occupy the centres of each of the cube faces. The formula of this compound is-

(A) AuCu                                                   

(B) $AuC{u}_2$

(C) $AuC{u}_3$                                                 

(D) None of these 

Copper metal has a face-centred cubic structure with the unit cell length equal to 0.361 nm. Picturing copper ions in contact along the face diagonal. The apparent radius of a copper ion is-

(A) 0.128                                         

(B) 1.42

(C) 3.22                                           

(D) 4.22

The unit cell dimensions of a cubic lattice (edges a, b, c and the angles between them, $\alpha , \beta , \gamma$ ) are 

1. a=b=c, $\alpha =\beta =\gamma =90°$

2. a=b$\ne$c, $\alpha =\beta =\gamma =90°$

3. a=b=c, $\alpha =\gamma =90°, \beta \ne 90°$

4. a$\ne$b$\ne$c, $\alpha =\beta =90°, \gamma \ne 90°$

At room temperature, sodium crystallises in a body centred cubic cell with a 4.24 $\stackrel{0}{A}$. The theoretical density of sodium is- (Atomic mass of sodium=23.0 g $mo{l}^{-1}$)

(A) $2.05 g c{m}^{-3}$                                         

(B) $3.45 g c{m}^{-3}$

(C) $1.00 g c{m}^{-3}$                                         

(D) $3.55 g c{m}^{-3}$

8 : 8 co-ordination of CsCl is found to change into 6 : 6
co-ordination on:

(a) applying pressure
(b) increasing temperature
(c) both (a) and (b)
(d) none of these

A solid PQ have rock salt type structure in which Q atoms are at the corners of the unit cell and P at edge. If the body centred atoms in all the unit cells are missing, the resulting stoichiometry will be-

(A) PQ                                               

 (B) $P{Q}_2$

(C) $P_3{Q}_4$                                             

(D) $P_4{Q}_3$

Frenkel defect is not found in the halides of alkali metals because alkali metals have

1. High electropositivity.

2. High ionic radii.

3. High reactivity.

4. Ability to occupy interstitial sites.

Analysis shows that an oxide ore of  nickel has formula  Ni_0.98O_1.00. The percentage of nickel as Ni³⁺ ions is nearly

1. 2

2. 96

3. 4.08

4. 98