The unit cell edge of a substance $(1$ monatomic cation: $1$ monatomic anion$)$ having a crystal lattice identical to that of sodium chloride has a length of $564\mathrm{.}9pm.$ The cation of the substance has a radius of $91pm.$ What is the diameter of the anion?

Part $1$

You are given the atomic radius of the cation and you want to determine the diameter of the anion. A salt structure contains $1$ cation and one anion on each edge. How many cation radii and how many anion diameters are one each edge?

Cation radii:

Anion diameters: