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HW1Solutions - lower coefficient of thermal expansion Since...

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MSE280B – Introduction to Materials Engineering Homework 1 – Solutions 1. (5 points) Ionization Energy is the energy required to remove the outermost electron from an atom and the metallic character of an atom is measured in terms of the ease of losing an outer electron and form a positive ion. From left to right in the periodic table, the ionic radius decreases and so the Ionization energy increases. Since a higher ionization energy means a lower tendency to give up electrons, the metallic character decreases. 2. (12 points) a) A has the deepest potential well and the highest bond energy. Since a higher bond energy implies a higher melting temperature, A will have the highest melting temperature. b) The curvature of the E-r curve at the point of minimum energy is related to the coefficient of thermal expansion. A higher curvature means a higher stiffness and thus a
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Unformatted text preview: lower coefficient of thermal expansion. Since C has the lowest curvature, it will have the highest coefficient of thermal expansion. c) Diamond has the highest bond energy, melting temperature and is very hard. Polyethylene, on the other hand, is very flexible and has a much lower melting point. Copper has intermediate values of melting temperature and elastic stiffness. From parts a and b, we can see that Diamond is curve `a’, Copper is `b’ and Polyethylene is `c. 3. (5 points) ZnO is more Ionic as it has a greater difference is electronegativity (X) between the two constituent atoms. (Electronegativity values obtained from Figure 7 in Callister) GaAs : X(As) – X(Ga) =2.0 – 1.6 = 0.4 ZnO: X(O) – X(Zn) = 3.5 – 1.6 = 1.9 4. Problem 2.9 from Callister Problem 2.11 from Callister Problem 2.14 from Callister...
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