For tetrahedral coordination number,the radius ratio $\frac{r_{c^+}}{r_{a^-}}$ is

An ionic compound has a unit cell consisting of $A$ ions at the corners of a cube and $B$ ions on the centres of the faces of the cube. The empirical formula for this compound would be

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

$A$ crystal is made of particles $X$ and $Y$. $X$ forms $fcc$ packing and $Y$ occupies all the octahedral voids. If all the particles along one body diagonal are removed,then the formula of the crystal would be:

In a simple cubic unit cell,how many unit cells share each lattice point located at the corner?

In the face-centred cubic $(FCC)$ lattice structure of gold,the closest distance between gold atoms is ('a' being the edge length of the cubic unit cell).