Question

Number of atoms in the unit cell of $Na ( BCC$ type crystal) and Mg (FCC type crystal) are respectively :

• A. 4,4
• B. 4,2
• C. 2,4
• D. 1,1

Answer 1

Answer: (C)

2,4

Answer 2

Na unit cell (body centred cubic) 8 corner atoms $\times \frac{1}{8}=1$ 1 atom placed inside the unit cell $=1$ Total atoms $=2$ Mg unit cell (Face centred cubic) 8 corner atoms $\times \frac{1}{8}=1$ 6 face atoms $\times \frac{1}{2}=3$ Total atoms $=4$