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Materials Science Homework - BIG PROBLEMS!

  1. Feb 12, 2012 #1
    I know there are set ways to post in this section, but I'm having so many problems with this class that I have to do it my own way. I decided to take Materials Science to help prepare me for graduate school and I am just struggling very much with this class. I haven't taken a physics class in 3 years, haven't taken a chemistry class in four. I have gone to talk to my professor, and he's useless to me. He doesn't explain anything, or even give me help, and so that doesn't do me any good. I've talked to a friend who graduated with a double major in Physics and Math and he said he was lost in this class so I'm a little nervous. I am asking for your help to help with me the basics because I seem to understand the newer stuff we've been doing much better. It's past my school's withdrawal period and I need to have the credits to graduate on time. I have had two homeworks, and I've been lost on both of them so I am hoping you guys can help me out a bit.

    Here are the problems from Homework 1
    1. Give the electron configurations for the following ions: P5+, P3-, and Ni2+.
    2. What type(s) of bonding would be expected for each of the following materials: solid
    xenon, bronze, and rubber?
    3. Calculate the force of attraction between a Ca2+ and an O2- ion the centers of which
    are separated by a distance of 1.25 nm.
    4. Below are listed the atomic weight, density, and atomic radius for three hypothetical
    alloys. For each determine whether its crystal structure is FCC, BCC, or simple cubic
    and then justify your determination.
    Alloy Atomic Weight (g/mol) Density (g/cm3) Atomic Radius(nm)
    A 43.1 6.40 0.122
    B 184.4 12.30 0.146
    C 91.6 9.60 0.137

    Here are the problems from Homework 2
    5. A hypothetical AX type of ceramic material is known to have a density of 2.10 g/cm3
    and a unit cell of cubic symmetry with a cell edge length of 0.57 nm. The atomic
    weights of the A and X elements are 28.5 and 30.0 g/mol, respectively. On the basis
    of this information, which of the following crystal structures is (are) possible for this
    material: sodium chloride, cesium chloride, or zinc blende? Justify your choice(s).
    6. Compute the atomic packing factor for the diamond cubic crystal structure (Fig.
    3.16).
    7. Sketch a monoclinic unit cell, and within that cell a [-101] direction.
    8. Below are shown three different crystallographic planes for a unit cell of some
    hypothetical metal. The circles represent atoms:


    (a) To what crystal system does the unit cell belong?
    (b) What would this crystal structure be called?
    (c) If the density of this metal is 18.91 g/cm3, determine its atomic weight.

    **I've uploaded both Homeworks so you can see them if it makes it easier**

    EDIT: any help, suggestions, links to learning places, would be fantastic. So far I haven't been able to do much learning with the way our course is taught (straight from PowerPoints) and I've been reading the book and taking notes. I just can't seem to wrap my head around crystal structures and so far that's what we've been doing. I would appreciate any help no matter how much or how little.
     

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  2. jcsd
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