Which of the following has a $4:2$ coordination number structure?

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

In zinc blende structure,the coordination number of $Zn^{2+}$ ion is

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

$A$ solid has a structure in which $W$ atoms are located at the corners of a cubic lattice,$O$ atoms are at the center of the edges,and $Na$ atoms are at the center of the cube. The formula for the compound is:

The edge lengths of a simple cubic $(sc)$ and a face-centered cubic $(fcc)$ unit cell are equal. The ratio of the volume occupied by atoms in these two structures is .....