An elemental crystal has a density of \(8570\,\text{kg m}^{-3}\). The packing efficiency is 0.68. The closest distance of approach between neighbouring atoms is \(2.86\,\text{\AA}\). What is the mass of one atom approximately?
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FCC crystals have packing efficiency of about 0.68.
Step 1: Packing efficiency \(0.68\) corresponds to FCC structure.
Step 2: Given interatomic distance matches that of copper crystal.
Step 3: Atomic mass of Cu \(\approx 63.5\,\text{amu}\).