Silicon and carbon are chemically very similar, both can form up to four chemical bonds. Silicon is the second most abundant element in Earth’s crust. But all kinds of life on Earth is based on carbon. So, why living organisms have not incorporated silicon into their biochemistry, like carbon?
Roald Hoffmann said “Poor silicon, abundant in the Earth, but rejected by the biosphere for its wondrous evolutionary tinkering,”
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Reasons why Silicon is not used as the base of life are:
- Reactions of Silicon are much slower than reactions of Carbon.
- Bonds between Si and Si or between Si and H are not as stable as the bond between Si and O.
- Molecules based on Si and H are not very stable in presence of water.
Some plants contain very small amounts of Si/silicides.
It could be the case on another planet.
Dear Dr Nabel,
Forgot to add the link.
Thank you very much for your reply
sorry my dear
http://tvtropes.org/pmwiki/pmwiki.php/Main/SiliconBasedLife
Reasons why Silicon is not used as the base of life are:
- Reactions of Silicon are much slower than reactions of Carbon.
- Bonds between Si and Si or between Si and H are not as stable as the bond between Si and O.
- Molecules based on Si and H are not very stable in presence of water.
The life on the earth is composed mainly of carbon, because carbon has four valences and it is possible for various bonds to be made.
In general, unlike carbon-carbon bonds, silicon-silicon bonds are quite unstable with almost no tendency to form double or triple bonds by pi bonds or sigma bonds at normal temperature and pressure. Therefore, most of the organosilicon compounds are organosilanes corresponding to alkanes of organic carbon compounds, and it is unlikely that silicon organisms are present in at least stars with similar environments to the Earth. Even assuming different environments, the compounds composed mainly of silicon are far fewer than those of carbon. Carl Edward Sagan says that it is natural to consider that extraterrestrial life forms are carbon organisms, and that silicon organisms are unrealistic.
Dear Dr. Ahmad Alrawashdeh,
The fact that silicon oxidizes to a solid is one basic reason as to why it cannot support life.
Mobile SIM cards made using silicon with some added impurities..
Being in the same column of the periodic table, it is expected that Si and C to have similar chemistry. However, Si has large atomic radius that prevents two Si atoms from advancing each other closely enough to gain much orbital overlap. In addition, Si-Si bonds are weak(177kj mol-1) and their multiple bonds are rarely stable. Si-O bond is very stable (369kj mol-1)and alternating chains of Si and O are inert (silicate mineral).
I agree with most of the answers above, saying that Si-based life forms are not possible! The reasons given by Andreas May are clearly the major reasons!
Just to add more; Si is more abundant on the Earth than carbon. If Si-based life forms are chemically possible, why we don't observe them today? Why it doesn't evolve in parallel with carbon-based life forms?
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