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1. Calculate the activation energy for vacancy formation in aluminum, given that the equilibrium number of vacancies at 500°C is 7.55 x1023 m3. 2. For a BCC single crystal, would you expect for a (100) plane to be greater or less than that for a (110) plane? Why? 3. Atomic radius, crystal structure, electronegativity, and the most common valence are tabulated in the following table for several elements; for those that are nonmetals, only atomic radii are indicated. Valence Crystal Structure FCC Electronegativity 1.9 +2 Element Cu с H o Ag AI 1.9 Atomic Radius (mm) 0.1278 0.071 0.046 0.060 0.1445 0.1431 0.1253 0.1249 0.1241 0.1246 0.1376 0.1387 Which of these elements would you expect to form the following with Cu: a. A substitutional solid solution having complete solubility. b. A substitutional solid solution of incomplete solubility. c. An interstitial solid solution. 1.5 1.8 +2 Со Cr 1.6 Fe FCC FCC HCP BCC BCC FCC FCC FCC HCP 1.8 古古古古古古古古土 Ni 1.8 +2 Pd 2.2 +2 Pt 2.2 +2 Zn 0.1332 1.6 +2