What is the two-dimensional coordination number of a molecule in a square close-packed layer?

What does the unit cell of $CsCl$ contain?

If the side length of a face-centered cubic $(fcc)$ unit cell of a metal is $400 \ pm$, the approximate radius of the metal atom in $pm$ is $(\sqrt{2} = 1.414)$.

For an ionic crystal of the type $AB$,the value of the limiting radius ratio is $0.40$. This value suggests that the crystal structure should be:

An example of a body-centered cubic $(BCC)$ crystal structure is:

How many total constituent particles are present in a simple cubic unit cell?