Question

In an ionic solid r(+) = 1.6 and r(-) = 1.864 . Use the radius ratio rule to determine the edge length of the cubic unit cell in .

• A. $4$
• B. $2\sqrt{3}$
• C. $3\sqrt{3}$
• D. $4/\sqrt{3}$

Answer 1

The correct option is A $4$

$r_{+}=1.6$ $r^{-}=1.864$

Along the body diagonal $2(r_{+}+r_{-})=a\sqrt{3}$

$2(1.6+1.864)=a\sqrt{3}$

$\Rightarrow a=4$