1. T F The hexagonal close packed (HCP) structure is best described as having ABCABCABC... stacking of atoms. 2. T F 3. T F 4. 5. T F 6. 7. TF 8. TF TF TF 9. T F 10. T F A solute or impurity atom that replaces or substitutes for the host atoms is known as an interstitial point defect. An edge dislocation can essentially be defined as an extra half plane of atoms in the crystal. Point defects such as vacancies do not occur at room temperature. Covalent bonding is usually stronger than metallic bonding. There are eight different crystal systems that describe space-filling periodic arrangements of atoms. Line defects include dislocations, grain boundaries, and vacancies. Fick's first law describes steady state diffusion. If a cubic material has a lattice parameter of 4 , the spacing between the (100) plane and the (200) plane will be 2 . In most alloys, vacancy diffusion occurs more rapidly than interstitial diffusion.