Reference Structures (Complete instructions for this lab are in the lab manual) Fill in the positions of the atoms in each of the unit cells you build, indicate the positions of the atoms on the model in the following diagrams and measure the length of the unit edge. For example, the face-centered cubic unit cell will have 00 3 1&5 2 In this figure each square represents one of the levels of a hands on model. The dark circles indicate the positions of the spheres on these levels. Note that the top and bottom layers (1 and 5) are identical. In this structure layers 2 and 4 are identical but keep in mind this will not always be the case. Cu unit cell edge: 3.612 A Complete the following figures: Body-centered cubic unit cell 1&5 2 Shortest Cr-Cr distance