Given : Molar mass = M = 27 g mol-1
Nature of crystal = cubic unit cell
Edge length = a = 405 pm = 4.05 × 10-8 cm
Density = ρ = 2.7 g cm-3
Nature of unit cell = ?
Hence the nature of unit cell = face-centred
cubic unit cell
Radius of Al atom = 125 pm
The nature of cubic unit cell is fcc.