What type of voids are formed when the spheres of the second layer are placed above the voids of the first layer (or vice versa) in the two-dimensional hexagonal close-packed arrangement?

Step-by-step solution

When the spheres of the second layer are placed above the voids of the first layer (or vice versa) in the two-dimensional hexagonal close-packed arrangement, tetrahedral voids are formed, as described in the paragraph.