Percentage of free space in cubic close packed structure and in body centered packed structure are respectively:

1. 48% and 26%

2. 30% and 26%

3. 26% and 32%

4. 32% and 48%

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Density/Formula/packing fraction/ Semiconductors
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Packing fraction of simple cubic crystal lattice is

1. 38%

2. 74%

3. 68%

4. 52.4%

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In which of the following crystals alternate tetrahedral voids are occupied

1. NaCl

2. ZnS

3. CaF2

4. Na2O

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In a metal oxide, the oxide ions are arranged in hexagonal close packing and metal ions occupy two third of the octahedral voids. The formula of the oxide is

1. MO

2. M2O3

3. MO2

4. M2O

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Density/Formula/packing fraction/ Semiconductors
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A crystal is made of particle X, Y & Z. X forms FCC packing, Y occupies all octahedral voids of X and Zoccupies all tetrahedral voids of X, if all the pariticles along one body diagonal are removed then the formula of the crystal would be –

(1) XYZ2

(2) X2YZ2

(3) X5Y4Z5

(4) X5Y4Z8

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Density/Formula/packing fraction/ Semiconductors
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In a hypothetical solid C atoms are found to form cubical close packed lattice. Aatoms occupy all tetrahedral vioids& B atoms occupy all octahedral voids. A and B atoms are of appropriate size, so that there is no distortion in CCP lattice of C atoms. Now if a plane as shown in the following figure is cut.

Then the cross section of this plane will look like.

(1)

(2)

(3)

(4)

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In hexagonal close packing of sphere in three dimensions.

(1) In one unit cell there are 12 octahedral voids and all are completely inside the unit cell.

(2) In one unit cell there are six octahedral voids and all are completely inside the unit cell.

(3) In one unit cell there are six octahedral void and of which three are completely inside the unit cell and other three are partially inside the unit cell.

(4) In one unit cell there are 12 tetrahedral voids, all are completely inside the unit cell.

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Density/Formula/packing fraction/ Semiconductors
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Diamond has face-centred cubic lattice. There are two atoms at (0,0,0) and $\left(\frac{1}{4},\frac{1}{4},\frac{1}{4}\right)$coordinates.The ratioof the carbon-carbon bond distance to the edge of the unit cell is

(1) $\sqrt{\frac{3}{16}}$

(2) 4

(3) $\frac{1}{4}$

(4) $\frac{1}{\sqrt{2}}$

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Density/Formula/packing fraction/ Semiconductors
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Spinel is an important class of oxides consisting of two types of metal ions with the oxide ions arranged inCCP pattern. The normal spinel has 1/ 8 of the tetrahedral holes occupied by one type of metal ion and 1/2 of the octahedral holes occupied by another type of metal ion. Such a spinel is formed by Zn2+, A13* and 02-with Zn2+ in the tetrahedral holes. If CCP arrangement of oxide ions remains undistorted in the presence of all the cations, formula of spinel and fraction of the packing fraction of crystal are respectively :

(1) ZnAl2O4 , 77%

(2) ZnAl2O4, 74%

(3) Zn2AlO4, 74%

(4) Zn3Al2O6,74%

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Introduction and Type of Crystal System
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What is the maximum number of layers of atoms in close packed planes that will lie within two imaginaryparallel planes having a distance between them of 13$\sqrt{\frac{2}{3}}$ R (where R is the radius of atom) in the coppercrystal (FCC) ? Consider the atoms to be within the parallel planes if their centresare on or within the two parallel planes.

(1) 5

(2) 6

(3) 7

(4) 8

Concept Questions :-

Introduction and Type of Crystal System