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Thread: Solid vs. Liquid vs. Gas

  1. #1 Solid vs. Liquid vs. Gas 
    Forum Freshman asxz's Avatar
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    What makes an element a solid/liquid/gas at room temperature? I know that it is something to do with the electrons and how they connect, but shouldn't that mean that each element with 8 electons in the outer shell is the same state?


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    Reptile Dysfunction drowsy turtle's Avatar
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    The intermolecular forces are what cause substances to be gas, liquid or solid at room temperature.

    IDIDs - instantaneous dipole - induced dipole

    this is where the electrons around an atom/molecule instantaneously and randomly move slightly more to one side than the other. The built up negative charge causes electrons on other nearby atoms to orientate themselves similarly, so that slight negative and positive charges between atoms attract. The bonds disappear just as quickly and randomly as they form.

    Bigger atoms/molecules, with greater area for these bonds to form and more electrons to move around, form stronger IDID bonds.


    PDPDs - permanant dipole - permanant dipole (polar bond)

    Because of electron shielding and nuclear charge, some elements attract electrons better than others (search for electronegativity and the pauling scale). In a covalent bond, one atom will therefore have the electrons in the bond closer to its nucleus than the other. This will make one atom slightly negative and the other slightly positively charged. These dipoles then arrange themselves between molecules and raise the boiling/melting point.

    E.G. Water - slightly positive hydrogen atoms attract slightly negative oxygen atoms, which is why its liquid.

    The number of polar bonds, and the extent of their polarity, affects the boiling point of a substance.


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