The metal has a fcc lattice. The edge length of the unit cell is 404 pm. The density of the metal is 2.72 g/cm3. The molar mass of the metal is NA=Avogadro's constant =6.02×1023mol-1.

Given, cell is fcc. So, Z = 4Edge length, a = 404 pm = 4.04 x 10-8 cmDensity of metal, d = 2.72 g/cm3           NA=6.02×1023 mol-1Molar mass of the metal, M = ? we know that density, d=Z×Ma3NA⇒M=d.a3NAZ =2.72×4.04×10-83×6.02×10234=27 g/mol