The most efficient packing of similar spheres is obtained in 

1. The simple cubic system and the body centered cubic system

2. The simple cubic system and the hexagonal close packed system

3. The face centered cubic system and the hexagonal close packed system

4. The body centered cubic system and the face centered cubic system

In a compound, atoms of element Y form ccp lattice, and those of element X occupy 2/3^rd of tetrahedral voids. The formula of the compound will be :-
1. X₃Y₄
2. X₄Y₃ 
3. X₂Y₃
4. X₂Y

A spinel is an important class of oxides consisting of two types of metal ions with the oxide ions arranged in ccp layers. The normal spinel has 1/8^th of the tetrahedral void occupied  by one type of metal and one half of the octahedral voids occupied by another type of metal ions. Such a spinel is formed by Zn²⁺, Al³⁺ and O^2- with Zn²⁺ in tetrahedral void. Give the simplest formula of the spinel.

1. ZnAl₂O₄

2. ZnAl₂O₃

3. ZnAlO

4. None of these

Close packing is maximum in the crystal lattice of:

1. simple cubic

2. face centred

3. body centred

4. none of these

Frenkel defect is noticed in:

1. AgBr

2. ZnS

3. Agl

4. All of the above

The density of KCl is 1.9893 g cm^-3 and the length of a side unit cell is 6.29082 Å as determined by X-ray diffraction. The value of Avogadro’s number calculated from this data is:-

1. 6.017 x 10²³

2. 6.023 x 10²²

3. 7.03 x 10²³

4. 6.01 x 10¹⁹

How many octahedral and tetrahedral holes are present per unit cell in a face centred cubic arrangement of atoms?

1. 8,4

2. 1,2

3. 4,8

4. 2 ,1

TiO₂ is a well-known example of:

1. Triclinic system.

2. Tetragonal system.

3. Monoclinic system.

4. None of the above.

For a solid with the following structure, the co-ordination number of the point B is:

1. 3

2. 4

3. 5

4. 6

The elements of symmetry in a crystal are:-

1. Plane of symmetry

2. Axis of symmetry

3. Centre of symmetry

4. All of the above