HW1_solutions_final - MSE 2620, Spring 09 Homework #1...

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MSE 2620, Spring ‘09 Homework #1 Problem 1: Bonding a) The ionization energy of Lithium is 5.39eV. What is the average distance of the 2s 1 electron from the nucleus? What assumptions did you make? b) There are three major types of bonding; metallic, covalent, and ionic. Describe each type and rank them according to bond strength. Using electrons explain why there is a general trend? Give an example of a material that does not follow this general trend. Bonus: Why does this particular material behave differently? Covalent bonding- Is a chemical bond formed by sharing of electrons by two atoms. Ionic bonding- Is a bond formed by the attraction between two oppositely charged ions, where the bonding electron spends most of its time around the negatively charged ion. Metallic Bonding-Is bonding by a “sea” of electrons around a crystal of positive ions. Book Bond Strength Covalent>Ionic> Metallic My Interpretation Ionic> Covalent> Metallic
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The reason why ionic and covalent bonds are typically stronger than metallic is the fact that when you take an atom away from the formers you create a very high energy unstable localized state where there is at least one unfilled orbital or an extra electron. However, for metallic bonds since it is a sea of electrons which means delocalization, when you take an atom away the crystal energy surrounding the site is not affected as much. Since most high temperature ceramics are oxide they necessarily have to be ionic in bonding. But since Diamond is the strongest material and has one of the highest melting points I think the book puts covalent bonding as stronger. However, if you look at typical organic bonds such as C-H you will notice that they have a relatively low melting point which corresponds to a weak covalent bond. c) From the kinetic theory of gases derive PV as a function of kinetic energy with a box that has dimensions of width = a, length = 2a, and thickness = 3a.
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d)
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HW1_solutions_final - MSE 2620, Spring 09 Homework #1...

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