A. Tantalum (Ta) has a BCC crystal structure, an atomic radius of 0.1430 nm, and an atomic weight of 180.94788 g/mol. Compute and compare its theoretical density with the experimental value found 16.65 g/cm³. B. Calculate the radius of an Aluminum (Al) atom, given that Al has an FCC crystal structure, a density of 2.7 g/cm³, and an atomic weight of 26.98 g/mol. C. The figure shows a unit cell for a hypothetical metal. (a) To which crystal system does this unit cell belong? (b) What would this crystal structure be called? (c) Calculate the density of the material, given that its atomic weight is 151 g/mol.