Which of the following statements is true ?

1. Piezo-electricity is due to net dipole moment

2. Ferro-electricity is due to alignment of dipoles in same direction

3. Pyro-electricity is due to heating polar crystals

4. All of the above

Which arrangement of electrons leads to anti-ferromagnetism?
(1)  ↑↑↑↑
(2)  ↑↓↑↓
(3) Both (a) and (b)
(4) None of these

Packing fraction of simple cubic crystal lattice is 

1. 38%

2. 74%

3. 68%

4. 52.4%

Silver metal crystallises in a cubic closest – packed arrangement with the edge of the unit cell having a length a = 407 pm. What is the radius of silver atom.

(1) 143.9 pm

(2) 15.6 pm

(3) 11.59 pm

(4) 13.61 pm

CsBr has a (bcc) arrangement and its unit cell edge length is 400 pm. Calculate the interionic distance in CsCl [CBSE 1993]

(1) 346.4 pm

(2) 643 pm

(3) 66.31 pm

(4) 431.5 pm

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, $\alpha =\beta =90°, \gamma \ne 90°$

An element crystallizes in a structure having FCC unit cell of an edge length 200 pm. If 200 g of this element contains 24 x 10²³ atoms, the density of the element is - 

1. 50.3 g/cc 

2. 63.4 g/cc

3. 41.6 g/cc 

4. 34.8 g/cc

Ionic radii of Mg²⁺ and O^2- ions are 66 pm and 140 pm respectively. The type of interstitial void and coordination number of Mg²⁺ ion respectively are

1. Tetrahedral, 12

2. Octahedral, 6

3. Tetrahedral, 6 

4. Octahedral, 8

CsCl has bcc structure with edge length 4.3 pm. The shortest inter ionic distance in between Cs⁺ and Br^- is :

1. 3.72 pm

2. 1.86 pm

3. 7.44 pm

4. 4.3 pm

An ionic compound AB has fluorite type structures. If the radius  ${\mathrm{B}}^{-}$ is 200 pm, then the ideal radius of ${\mathrm{A}}^{+}$ would be :

1. 82.8 pm

2. 146.4 pm

3. 40 om

4. 45 pm