Q: Fraction of total volume occupied by atoms in a simple cubic cell is

(A) π/2

(B) √3π/2

(C) √2π/2

(D) π/6

Ans: (D)

Sol: In simple cubic arrangement, no. of atoms = 1

a = 2r

Packing fraction = Volume occupied by one atom / Volume of unit cell

$\large = \frac{\frac{4}{3}\pi r^3}{a^3} $

$\large = \frac{\frac{4}{3}\pi r^3}{(2r)^3} = \frac{\pi}{6} $