Chemistry - Solid State Question with Solution | TestHub

In a BCC unit cell, the number of atoms per unit cell is $Z=2$, so option (A) is correct.

Atoms touch along the body diagonal, therefore the relation is $4r=\sqrt{3}a$, so option (B) is correct.

The packing efficiency (packing fraction) of BCC is about 68% (0.68), so option (D) is correct.

The coordination number of a BCC lattice is 8, not 6.

Therefore, the statement C.N. = 6 is incorrect.

Hence, the correct answer is Option (C).