Question

Sodium metal crystallises in bcc lattice with the cell edge $a=42.29\stackrel{o}{A}$. What is the radius of sodium atom?

Answer 1

In a body-centered cubic lattice, atoms touch along the body diagonal of the cube. Thus

$4r=\sqrt{3}a$

$r=\frac{\sqrt{3}a}{4}$

$r=\frac{\sqrt{3}\times 42.29}{4}$ = 18.31 $A^o$