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Molecular Solid vs Network Covalent Solids

  1. May 18, 2015 #1
    1. The problem statement, all variables and given/known data
    I'm having trouble figuring out if a solid is a molecular solid or network covalent solid.

    Classify the following as a network covalent solid or a molecular solid:
    1. CO2
    2. SiO2

    2. Relevant equations
    Molecular solid held together by intermolecular forces
    Covalent network solids are held together by covalent bonds.

    3. The attempt at a solution
    I know that CO2 is a molecular solid and SiO2 is a network covalent solid, but I'm not sure how I would figure that out. They both have two oxygen atoms, and carbon and silicon have the same number of valence electrons. What makes them different types of solids then?
     
  2. jcsd
  3. May 18, 2015 #2

    James Pelezo

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    Gold Member

    This is a topic that, honestly, can't be reduced to a few rules. It is easy to say CO2 is this, or SiO2 that, but to understand what you need under "The attempt at a solution" it requires a comprehensive understanding of how solid state structures are classified & how different classifications of structures interact. The statements under "Relevant Equations" above, are correct, but is only a part of the 'big picture' that you need understand in order to ID the classification of solids from formulas. I might suggest looking up 'The Solid State' in a reputable college chemistry text and spend quality time reviewing
    - classification of types of solids,
    - properties of solids that affect melting point, hardness & conductivity,
    - crystalline structure and how it is defined, and
    - structures of specific types of crystalline solids.
    I wish I could say your question has a simple answer or rule, but it does not. It will be a time consuming effort to develop a good understanding, but well worth the effort. Lots of luck. :-)
     
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