In an ionic oxide,the oxide anions form an $hcp$ arrangement,while the metal cations occupy $\frac{2}{3}$ of the octahedral voids. Determine the formula of this oxide.

In a solid,$B^{-}$ ions occupy corners of a cube forming $ccp$ structure. If $A^{+}$ ions occupy half the tetrahedral voids,the formula of the solid is:

Calculate the total number of tetrahedral and octahedral voids in $0.4 \ mol$ of a compound having such voids in it.

$A$ two-dimensional solid pattern formed by two different atoms $X$ and $Y$ is shown below. The black and white squares represent atoms $X$ and $Y,$ respectively. The simplest formula for the compound based on the unit cell from the pattern is

$A$ metal crystallizes in a lattice having $AB AB AB$ sequence of layers. This arrangement of spheres corresponds to which type of packing,and what is the percentage of empty space (void volume) in this lattice?

The limiting radius ratio for a tetrahedral void is: