A cubic structure is formed where atoms of element $X$ are occupied at corner of cube and also at face centers. Atoms of element $Y$ are present at body center and at the edge centers. If all the atoms are removed along a plane passing through the middle of the cube (bisecting the four edges), the formula will become

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 $\sqrt{6}=2.4$ )