Lithium metal crystallises in a body centred cubic crystal. If the length of the side of the

unit cell of lithium is 351 pm, the atomic radius of the lithium will be

1. 240.8 pm

2. 151.8 pm

3. 75.5 pm

4. 300.5 pm

The incorrect statement among the following is:

If 'a' stands for the edge length of the cubic systems: simple cubic, body centered cubic and face centered cubic, then the ratio of radii of the spheres in these systems will be respectively,

$\left(\mathrm{a}\right)<mspace\; width="1em"></mspace>\frac{1}{2}\mathrm{a}:<mspace\; width="1em"></mspace>\frac{\sqrt{3}}{4}\mathrm{a}:\frac{1}{2\sqrt{2}}\mathrm{a}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>\left(\mathrm{b}\right)<mspace\; width="1em"></mspace>\frac{1}{2}\mathrm{a}:\sqrt{3}\mathrm{a}:\frac{1}{\sqrt{2}}\mathrm{a}$
$\left(\mathrm{c}\right)<mspace\; width="1em"></mspace>\frac{1}{2}\mathrm{a}:\frac{\sqrt{3}}{2}\mathrm{a}:\frac{\sqrt{2}}{2}\mathrm{a}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>\left(\mathrm{d}\right)<mspace\; width="1em"></mspace>1\mathrm{a}:\sqrt{3}\mathrm{a}:\sqrt{2}\mathrm{a}$

Percentage of free space in a body centered cubic unit cell is

(1) 30%                       

(2) 32%

(3) 34%                       

(4) 28%

With which one of the following elements silicon should be doped so as to give p-type of semiconductor?
(1) Germanium

(2) Arsenic

(3) Selenium

(4) Boron

The fraction of total volume occupied  by the atoms present in a simple cube is:

$$\begin{gathered} 1.<mspace\; width="1em"></mspace>\mathrm{\pi }/6<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace> \\ 2.<mspace\; width="1em"></mspace>\mathrm{\pi }/3\sqrt{2} \\ 3.<mspace\; width="1em"></mspace>\mathrm{\pi }/4\sqrt{2}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace> \\ 4.<mspace\; width="1em"></mspace>\mathrm{\pi }/4 \end{gathered}$$

A low melting point is expected for solid

1. Ionic solids 

2. Metallic solids 

3. Molecular solids 

4. Covalent solids 

Copper crystallises in a face-centred cubic lattice with a unit cell length of 361 pm. What

is the radius of copper atom in pm?

1. 128

2. 157

3. 181

4. 108

The number of octahedral void(s) per atom present in a cubic close-packed structure is

1. 1

2. 3

3. 2

4. 4

A metal cryszallizes with a face-centered cubic lattice. The edge of the unit cell is 408

pm. The diameter of the metal atom is

1. 288 pm

2. 408 pm

3. 144 pm

4. 204 pm