In a solid ‘AB’ having the NaCl structure, ‘A’ atoms occupy the corners of the cubic unit cell. If all the face – centred atoms along one of the axes are removed thye the resultant stoichiometry of the solid is


Correct option is



There are 6 A atoms on the face centres removing face centred atoms along one of the axes means removal of 2 A atoms.

Now, number of A atoms per unit cell


                        (corners)              (face - centred)

Number of B – atoms per unit cell


                        (edge centred)   (body centred)

Hence, the resultant stoichiometry is A3 B4.



The number of sphere contained (i) in one body centred cubic unit cell and (ii) in one face centred cubic unit cell, is


CsBr crystal has bcc structure. It has an edge length of 4.3. the shortest interionic distance between Cs+ and Br –  ions is



The number of atoms in 100 g of an fcc crystal with density,

d = 10g/ cm3 and cell edge equal to 100 pm, is equal to


The number of unit cell in 58.5 g of NaCl is nearly


Analysis shows that an oxide ore of nickel has formula Ni0.98O1.00. The percentage of nickel as Ni3+ ions is nearly


In orthorhombic, the value of a, b and c are respectively 4.2, 8.6 and8.3. given the molecular mass of the solute is 155 g mol-1 and that of density is 3.3 g/cc, the number of formula units per unit cell is


A solid has a structure in which ‘W’ atoms are located at the corner of a cubic lattice ‘O’ atoms at the centre of edge and Na atoms at the centre of the cube. The formula for the compound is


Ferrous oxide has a cubic structure and each edge of the unit cell is 5.0. Assuming density of the oxide as 4.0 g/cm-3, then the number of Fe2+ and O2- ions present in each unit cell will be


The following is not a function of an impurity present in a crystal



The pyknometric density of sodium chloride crystal is

2.165 × 103 kg m-3, while its X – rays density is 2.178 × 103kg m-3

The fraction of unoccupied sites in sodium chloride crystal is