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Carbon is the basis of organic materials in large part due to it's four valence electrons. Silicon also happens to have four valence electrons as well but does not serve as a basis for a large set of compounds on the level of Organic compounds.

Given the four valence electrons nature of both elements, why can't Silicon serve as a base for a numerous swath of compounds like Carbon does for Organic compounds?

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    $\begingroup$ OK, we've come one level up. Now, silicon surely can and does serve as a base for a numerous swath of compounds. What was your question again? $\endgroup$ Nov 25, 2018 at 0:11
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    $\begingroup$ The key issue is that carbon-carbon bonds are stable which allows a very rich chemistry of complex compounds we call organic chemicals. silicon-silicon bonds are not and the variety of silicates (containing a range of structures built on Si-O-Si bonds), while large, is nothing like as varied as organic chemicals and not apparently sufficient to support enough complexity to support life. $\endgroup$
    – matt_black
    Nov 25, 2018 at 0:45

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Silicon has a weaker affinity for electrons than Carbon does because its valence electrons are farther away from its nucleus, so it tends to act a little bit more like a metal - meaning Silicon is more likely to oxidize (give away its valence electrons, like a metal) than to reduce (fill its valence shell, like nitrogen, oxygen, etc.) Carbon just happens to be perfectly kind of "ambivalent" on whether it oxidizes or reduces, allowing it to form essentially limitless chains of single, double, and triple-bonds to itself and to nearly any other element, allowing the absurdly complex structures necessary to support life.

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Silicon cannot be an effective substitute for Carbon.

This article by Raymond Dessy explains why. Four key points are summarized below. The reason life forms are mentioned is to address the comment from @matt_black.

  1. Silicon oxidizes to the solid Silica, thus this would post waste disposal problems for life forms.
  2. Silicon does not form many compounds that have handedness. In other words, it cannot process or store energy in a stable process like Carbon based enzymes can. Thus the energy could not sustain a living organism.
  3. The Silicon analogs of carbon compounds cannot be formed as they are too unstable or too reactive despite the reagants available to Chemists. This is supported by @matt_black's comment.
  4. The narrow range of temperature and pH levels where most of life processes occur are suitable for Carbon compounds, but not Silicon.
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  • $\begingroup$ OP wasn't asking why silicon cannot be a substitute for carbon though. Edit: Oh... hi OP. $\endgroup$ Dec 10, 2018 at 22:19
  • $\begingroup$ Silicon very commonly forms at least one chiral compound. Quoting Wikipedia: "Although optical activity is normally thought of as a property of fluids, particularly aqueous solutions, it has also been observed in crystals such as quartz (SiO2) ... Rotation of the plane of polarization is observed due to the relative rotation between crystal planes, thus making the crystal formally chiral as we have defined it." $\endgroup$ Jan 22, 2021 at 13:17

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