Rhenium oxide crystallizes with a structure that has a primitive cubic lattice, as shown here. In the

Question:

Rhenium oxide crystallizes with a structure that has a primitive cubic lattice, as shown here. In the image on the left, the sizes of the ions have been reduced to show the entire unit cell.
(a) How many atoms of each type are there per unit cell?
(b) Use the ionic radii of rhenium (0.70 Ã…) and oxygen (1.26 Ã…) to estimate the length of the edge of the unit cell.
(c) Use your answers to parts (a) and (b) to estimate the density of this compound.