Iron exhibits bcc structure at room temperature. Above 900°C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900°C (assuming molar mass and atomic radii of iron remains constant with temperature) is

In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion (Ca²⁺) and fluoride ion (F^$$-$$) are

The ionic radii of A⁺ and B^$$-$$ ions are 0.98 $$ \times $$ 10^$$-$$10 m and 1.81 $$ \times $$ 10^$$-$$10 m. The coordination number of each ion in AB is

Lithium has a bcc structure. Its density is 530 kg m^$$-$$3 and its atomic mass is 6.94 g mol^$$-$$. Calculate the edge length of a unit cell of lithium metal. (N_A = 6.02 $$ \times $$ 10²³ mol^$$-$$1)