An alloy of Cu, Ag and Au is found to have Cu forming the simple cubic closed packed lattice. If the Ag atoms occupy the face centres and Au is present at the body centre, the formula of the alloy will be


Correct option is

CuAg3 Au


Cu atoms are at eight corners of the cubic. Therefore, the number of Cu atoms in the unit cell = 8/8 = 1.

Ag atoms are at the face – centre of six faces. Therefore, its share in the unit cell = 6/2 = 3.

Au atoms are at the body centre,

∴ the number of Au atoms = 1

∴ The formula of the alloy is CuAg3 Au.



A solid AB has the NaCI structure. If radius of cation A+ is 120 pm, the maximum possible value of the radius of the anion B- is


CsCl crystallizes in a cubic lattice that has a Cl- at each corner and Cs+ at the centre of the unit cell. What is the value of edge length a of the cube?  



KCI crystallises in the same type of lattice as does NaCI.


The ratio of the side of the unit cell for NaCI to that for KCI is


The unit cell of aluminum is a cube with an edge length of 405 pm. The density of aluminum is 2.70 g cm-3. The type of unit cell is


A binary solid X+ Y- has a zinc blende structure with Y- ions forming the lattice and X+ ion occupying 25% tetrahedral sites. The formula of the solid is


Gold (at wt. 197g mol-1) crystallises is a cubic closest packed structures (the face – centred cubic) and has a density of 19.3g/cm2. Its atomic radius is


Calcium metal crystallizes in fcc lattice with edge length 556 pm. Calculate the density (in g cm-3) of metal if it contains 0.2% Schottky defects.


Which of the following statements about amorphous solids is incorrect?


If the radius ratio is in the range of 0.414 – 0.732, then the coordination number will be


Quartz is a crystalline variety of