A compound can crystallise in two forms $\alpha$ and $\beta$ which are fcc and bcc, respectively. The $\alpha$-form has side length of 2 pm and the $\beta$-form has side length of 4 pm . The ratio of their density $\frac{\rho_\alpha}{\rho_\beta}$ is

The angle between (100) and (110) planes of FCC lattice is

In a bcc lattice having the edge length of 200 pm , the cation has the radius of 70 pm . The radius ratio of $\frac{r^{+}}{r^{-}}$is (Given, $\sqrt{2}=1.4, \sqrt{3}=1.7$ and $\sqrt{6}=2.4$ )

Copper crystallises in ccp arrangement and accepted value of metal ion radius was found to be $1.14 \mathop {\rm{A}}\limits^{\rm{o}}$. Calculate the density of copper in grams per cubic centimetre. (Atomic weight of copper is 64 , $N_A=6 \times 10^{23}$ )