Copper has the fcc crystal structure. Assuming an atomic radius of 130pm for copper atom (Cu = 63.54): (a) What is the length of unit cell of Cu? (b) What is the volume of the unit cell? (c) How many atoms belong to the unit cell? (d) Find the density of Cu.
Answer -
As we know p = Z × M / NA × a3 (a) for fcc structure 4r = √2 a a = 2√2r =2√2 × 130 pm = 367.64 pm (b) volume of unit cell = a3 = (367.64 × 10–10 cm)3 = 4.968 × 10–23 cm3 (c) n = 4 (d) p = 4 × 63.54 / 6.023 × 1023 × (3.67 × 10–8 cm3)3 = 8.54 gm / cm3
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