A metallic element has a cubic lattice. Each edge of the unit cell is 2 2Ao. The density of the metal is 2.5 g cm-3. The unit cells in 200 g of metal are

Number of unit cells =mass of metalmass of one unit cell Given, edge length of unit cell =2Ao=2×10−8cmMass of metal = 200 gDensity of metal = 2.5 g cm-3Volume of unit cell = (edge length)3 =2×10−83=8×10−24cm3Mass of one unit cell - volume x density=8×10−24×2.5=20×10−24∴Number of unit cells in 200 g metal= mass of metal  mass of one unit cell =20020×10−24=1.0×1025