Schottky defects occurs mainly in electrovalent compounds where
positive ions and negative ions are of different size
positive ions and negative ions are of same size
positive ions are small and negative ions are big
positive ions are big and negative ions are small
An ion leaves its regular site occupy a position in the space between the lattice sites is called
Frenkel defect
Schottky defect
impurity defect
vacancy defect
A metallic element has a cubic lattice. Each edge of the unit cell is 2 . The density of the metal is 2.5 g cm -3 . The unit cells in 200 g of metal are
1
Which among the following solids crystallises as a face centred cube?
Iron
Rubidium
Uranium
Platinum
Which metal among the following has the highest packing efficiency?
Iron
Tungsten
Aluminium
Polonium
Which metal crystallises in a simple cubic structure?
Polonium
Copper
Nickel
Iron
A.
Polonium
In a simple cubic structure, the spheres are not packed as closely as they could be, and they only fill about 52% of the volume of the container. This is relatively inefficient arrangement and only one metal (polonium, Po) crystallises in a simple cubic structure. For a polonium atom in a simple cubic array, the coordination number is six.
An element crystallising in body centred cubic lattice has an edge length of 500 pm. If its density is 4 g cm-3, the atomic mass of the element (in g mol-1) is (consider NA = 6 × 1023)
100
250
125
150
Aluminium (atomic mass = 27) crystallises in a cubic system with edge length of 4 Å. Its density is 2. 7 g cm-3 The number of aluminium atoms present per unit cell is
5
6
4
2
For two isomorphous crystals A and B, the ratio of density of A to that of B is 1.6 while the ratio of the edge length of B to that of A is 2. If the molar mass of crystal B is 200 g mol-1, then that of crystal A is
240 g mol-1
40 g mol-1
80 g mol-1
160 g mol-1