Which of following unit cell has the smallest atomic packing factor? (a) BCC unit cell (b) FCC unit cell (c) SC unit cell (d) HCP unit cell

(c) SC unit cell

Explanation:

BCC (Body centered cubic) : In this one atom is present at center of the cell and one at each corner the packing factor of the BCC is 68% FCC (Face centered cubic) : In this one atom is present at the each faces and one at each corner the packing factor of FCC is 74 % SC (Simple cubic) : In this the atoms are present only at corner its packing factor is 52.4 % HCP (Hexagonal closed pack) its packing factor is 74.04 %

So from above discussion it is clear that simple cubic has smallest packing factor