In $FCC$ lattice,alternate tetrahedral voids are occupied in which of the following?

Which one possesses an antifluorite structure?

Which of the following is a $1:2$ type compound?

The crystal structure of $AB$ is of $NaCl$ type. If the radius of the $A^+$ ion is $x \ pm$ and the radius of the $B^-$ ion is $y \ pm$, then the edge length of the unit cell will be ..........

In the fluorite structure,the coordination number of $Ca^{2+}$ ion is

In a crystal of substance $A_xB_y$,$A$ atoms are present at each corner of the face-centered cubic $(FCC)$ unit cell,and $B$ atoms are present at each face center. What is the correct formula of the substance $A_xB_y$?