Question

Sodium crystallizes in bcc arrangement with the interfacial separation between the atoms at the edge $53\, pm$. The density of the solid is

• A. 1.23 g/cc
• B. 485 g/cc
• C. 4.85 g/cc
• D. 123 g/cc

Answer 1

Answer: (A)

1.23 g/cc

Answer 2

Given, $a-2\, r=53\, pm$ For bcc structure, $4 r=\sqrt{3} a$ or $2 r=\frac{\sqrt{3}}{2} a$ $\Rightarrow a-\frac{\sqrt{3}}{2} a=53$ $\therefore a=395.6 \, pm$ Density $(d)=\frac{Z M}{N_{a} a}$ $d =\frac{2 \times 23}{6.023 \times 10^{23} \times(3.956)^{3} \times 10^{-24}}$ $=1.23 \,g / cc .$