Niobium crystallises in body-centred cubic structure. If density is 8.55 g cm-3, calculate atomic radius of niobium using its atomic mass 93 u.
Given Density = 8.55 gcm-3
Let the length of the edge = a cm
Number of atoms per unit cell, Z = 2
Atomic mass M = 93 u
From the formula , density = ZxM/a3 x N0, we get
8.55 = 2 x 93/a3 x 6.022 x 1023 = 36.12 x 10-24 cm3
Now edge length,a = (36.12 x 10-24)1/3 = 3.306 x 10-8 cm
Now radius in body centered cubic, r = √3/4 a
Putting the value of a, we get .r = 1.431 x 10-10 m
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