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No, glass is a ceramic and is composed of oxides, which is vastly different from metals in its structure. The above diagrams are appropriate for metals but not for ceramics. Silica glasses have short-range order, so it's best to think of them as rings of alternating Si and O atoms. Whereas an ice crystal would be formed of perfect hexagons, these rings of Si and O do not have such a pattern, thus making it have no long-range order. What tempering glass does is it induces stresses within the glass due to thermal expansion. By rapidly cooling the outside of the glass, you do not allow it time to contract. Thus, when the glass inside cools more slowly, it attempts to contract and starts to pull at the surface of the glass (although these are referred to as compressive stresses). It makes the glass stronger because now when you want to break the piece of glass, you must first overcome these stresses (thus taking it to a "neutral" state) and then can you "begin to break the glass", if you will. Ion exchange does a similar thing, but instead it induces these stresses by taking advantage of the difference in size between Na and K ions. These ions are very large compared to Si and O and sit in the interstitial sites (that is, the center of the SiO2 rings).
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Jan 24, 2011