Question

A solid has a bcc structure. If the distance of closest approach between the two atoms is $1.73\mathring{A}$. The edge length (in pm) of the cell is:

• A. $200pm$
• B. $\frac{\sqrt{3}}{\sqrt{2}}pm$
• C. $142.2pm$
• D. $\sqrt{2}pm$

Answer 1

The correct option is A $200pm$

Distance of closest approach between two atoms $=\sqrt{3}=1.73$ (given)

Let the side length be $a$.

$l=\frac{a\sqrt{3}}{2}=$ Distance of closest approach.

$\frac{a\sqrt{3}}{2}=\sqrt{3}\mathring{A}$

$\Rightarrow a=2\mathring{A}$

$a=200pm$