In chrysoberyl, a compound containing beryllium, aluminium and oxygen, oxide ions form cubic close packed structure. Aluminium ions occupy $$\frac{1}{4}$$th of octahedral voids. The formula of the compound is

The correct statement regarding defects in solid is

A metal crystallises in bcc lattice with unit cell edge length of $$300 \mathrm{~pm}$$ and density $$615 \mathrm{~g~cm}^{-3}$$. The molar mass of the metal is

A metal crystallises in face centred cubic structure with metallic radius $$\sqrt{2} \mathop A\limits^o$$. The volume of the unit cell (in $$\mathrm{m}^3$$ ) is