Question

Sodium has body centred packing. If the distance between two nearest atoms is 3.7 Å, then its lattice parameter is.

• A. 4.8 Å
• B. 4.3 Å
• C. 3.9 Å
• D. 3.3 Å

Answer 1

Answer: (B)

4.3 Å

Answer 2

For bcc packing, distance between two nearest atoms $d = 2r = 2\left( \frac{\sqrt{3}a}{4} \right)$

⇒ Lattice constant $a = \frac{2d}{\sqrt{3}} = \frac{2 \times 3.7}{\sqrt{3}} = 4.3Å$.