ENGR 220 Homework Problems Week 2 - Chapter 3 1. What is the difference between atomic structure and crystal structure? 2. If the atomic radius of aluminum is 0.143 nm, calculate the volume of its unit cell in cubic meters. 3. Show that the atomic packing factor for BCC is 0.68. 4. Niobium (Nb) has a BCC crystal structure, an atomic radius of 0.143 nm and an atomic weight of 92.91 g/mol. Calculate the theoretical density for Nb. 5. Calculate the radius of a vanadium atom, given that V has a BCC crystal structure, a density of 5.96 g/cm3, and an atomic weight of 50.9 g/mol. 6. The atomic weight, density, and atomic radius for three hypothetical alloys are listed in the following table. For each determine whether its crystal structure is FCC, BCC, or simple cubic and then justify your determination. Alloy Atomic Weight (g/mol) Density (g/cm3) Atomic Radius (nm) A 77.4 8.22 0.125 B 107.6 13.42 0.133 C 127.3 9.23 0.142 7. A hypothetical metal has the BCC crystal structure, a density of 7.24 g/cm3, and an atomic weight of 48.9 g/mol. The atomic radius of this metal is: (A) 0.122 nm (C) 0.0997 nm (B) 1.22 nm (D) 0.154 nm 1