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2. 5/5 points | Previous Answers NCSUGenChem102LabV1 6.POST.02. In modeling solid-state structures, atoms and ions are most often modeled as spheres. A structure built using spheres will have some empty, or void, space in it. A measure of void space in a particular structure is the packing efficiency , defined as the volume occupied by the spheres divided by the total volume of the structure. Given that a solid crystallizes in a body centered cubic structure that is 3.83 on each side, answer questions (a)-(e). (1 = 1 10 -10 m.) (a) How many total atoms are there in each unit cell?
(b) What is the volume of one unit cell in 3 ? 3
(c) Assuming that the atoms are spheres and the radius of each sphere is 1.66 , what is the volume of one atom in 3 ? ( V sphere = 4/3 π r 3 .) 19.2 3
(d) Therefore, what volume of atoms are in one unit cell? 3
(e) Based on your results from parts (b) and (d), what is the packing efficiency of the solid expressed as a percentage? %
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3. 5/5 points | Previous Answers NCSUGenChem102LabV1 6.POST.03. Many metals pack in cubic unit cells. The density of a metal and length of the unit cell can be used to determine the type for packing. For example, polonium has a density of 9.19 g/cm 3 and a unit cell side length a of 3.37 (1 = 1 10 -8 cm.) (a) How many polonium atoms are in exactly 1 cm 3 . ?

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