Sodium metal crystallizes in bcc lattice with cell edge $=4.29 \stackrel{0}{A}$. The radius of sodium atom will be-

(1) 1.50 $\stackrel{0}{A}$                                                 

(2) 1.86  $\stackrel{0}{A}$

(3) 2.80 $\stackrel{0}{A}$                                               

(4) None of these 

The space lattice of graphite is

1. Cubic                                     

2. Tetragonal

3. Rhombic                                 

4. Hexagonal

The edge length of the cube is 400pm. Its body diagonal would be-

(1) 500 pm                                         

(2) 693 pm

(3) 600 pm                                           

(4) 566pm

A metallic element exists as a cubic lattice. Each edge of the unit cell is 2.88 $\stackrel{0}{A}$. The density of the metal is 7.20 g $c{m}^{-3}$. How many unit cell will be present in 100 g of the metal -

(1) $6.85\times {10}^2$                             

(2) $5.82\times {10}^{23}$

(3) $4.37\times {10}^5$                             

(4) $2.12\times {10}^6$

Iron crystallizes in a b.c.c. system with a lattice parameter of 2.861 $\stackrel{0}{A}$. Calculate the density of iron in the b.c.c. system (Atomic weight of Fe = 56, $N_A=6.02\times {10}^{23}mo{l}^{-1}$)

(1) 7.92g $m{l}^{-1}$                                   

(2) 8.96g $m{l}^{-1}$

(3) 2.78g $m{l}^{-1}$                                     

(4) 6.72g $m{l}^{-1}$

An alloy of copper, silver, and gold is found to have copper constituting the ccp lattice. If silver atoms occupy the edge centers and gold is present at the body center, the alloy has a formula-

(1) $C{u}_{4}A{g}_{2}Au$                               

(2) $C{u}_{4}A{g}_{4}Au$

(3) $C{u}_{4}A{g}_{3}Au$                               

(4) $CuAgAu$

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

Iodine crystals are classified as-

1. Metallic solids.                                  

2. Ionic solids.

3. Molecular solids .                                 

4. Covalent solids.

A solid PQ have rock salt type structure in which Q atoms are at the corners of the unit cell. 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) $P_4{Q}_3$

At room temperature, sodium crystallizes in a body-centered 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) $3.55 g c{m}^{-3}$