NAME PRINT ________________________ INTRODUCTION TO MATERIAL SCIENCE MSE-150 QUIZ 2 I PLEDGE MY HONOR THAT I HAVE NEITHER GIVEN OR RECEIVED AID ON THIS EXAMINATION. I FURTHER PLEDGE THAT, IF I HAVE REASON TO SUSPECT THAT THE CODE HAS BEEN VIOLATED, I HAVE TAKEN OR WILL TAKE ACTION AS OUTLINED IN THE CODE. SIGNATURE _________________________ (1 point each) True or False T Ionic bonding is a non-directional primary bond resulting from electrostatic forces.
F Covalent bonding is a directional primary bond resulting from sharing of delocalized valence electrons. F Cations are typically larger than anions.
F The atomic packing factor (APF) of the face centered cubic (FCC) structure is less than the APF of the hexagonal close packed structure (HCP). F As the difference in the electronegativities between the elements in a ceramic compound decreases the bond character more is ionic than covalent. T T Polymers typically contain both covalent and secondary bonding. The non-directional nature of the metallic bond results in crystals with high coordination numbers.
(1 point each) Label the following as characteristics of strong bonds (S) or weak bonds (W). W S W S W low melting point short bond length low hardness small thermal expansion coefficient low elastic modulus
(3 points) What are the coordination numbers (number of nearest neighbors) for FCC, HCP, and body centered cubic (BCC) crystal structures? FCC 12 HCP 12 BCC 8 (2 points) How many atoms are contained inside of the unit cell for FCC and BCC crystals? FCC 4 atoms BCC 2 atoms (3 points) Calculate the atomic radii for copper (FCC with a = 0.361 nm). Use the correct number of significant figures for the correct answer. a) 0.1565 nm b) 0.157 nm c) 0.128 nm d) 0.1276 nm