I heard that silicon has four bonds directed to the corners of a tetrahedron, just like carbon. Therefore there are so many carbon products in organic chemistry, are there analogous compounds to each of these for silicon? In other words like ethyl or maybe it is methyl, is there a silicon analogue to this whereby we have silicon with four hydrogens? If not, how come? And what about a complete world of life forms both plant and animal that are all based on silicon instead of carbon?Would the creatures be running around with quarz plates all over them like in science fiction?
Because silicon has an extra layer of electrons, the bonds it forms are much weaker than those formed by carbon. That’s pretty much a dealbreaker.
There have been some theoretical constructs for silicon-based life (for instance, they can’t breathe oxygen – their waste products would be silicon dixode, which would quickly clog up their lungs), but it’s considered highly unlikely that the proper conditions would occur.
So silicon-based life is unlikely, unless you consider the shower scene in Starship Troopers. 
Even with the limitations pointed out by the above posters, my gut feel is that the near-infinite lab bench of the universe could find a way to make life from silicon, if carbon is unavailable.
Which girl are you referring to? The matched pairs all looked prettty non-pumped and “natural”.
How about a solar-powered, self-replicating AI ‘computer’, using solid-state components. Not quite silanes, but does not take too much of a stretch of imagination.
Didn’t one of Asimov’s Wendell Urth stories postulate a silicon-based life form?
I read a story in the local paper about 5 years ago involving a scientist who believed that there may be silicon-based single-celled organisms deep within the Earth’s mantle (or possibly the core). My memory’s pretty spotty, but you can at least be comforted by the fact that it’s certainly been considered before.
The origin of carbon based life forms was in a primordial soup where carbon atoms could slosh around and their affinities to form organic compounds could start their long evolution.
The equivalent primoridal soup for silicon based life forms would be solid rock, providing a lot less flexibility for silicon’s affinities.
As noted above, there’s been a lot of speculation about silicon=based life forms in sf (The Horta! – “Devil in the Dark” on the old Star Trek, for one), not to mention about life in a chlorine atmosphere (you can burn a candle in pure chlorine, apparently). My take on this is that you probly could have life in these odd situations, but it would not be Life As We Know It. It might be different in size scale, or in time scale, or be in a form we don’t recognize at all. (Not animal, not vegetable, not predator or prey or parasite. Just Something Else.)
For the record, Stanley G. Weinbaum, in his classic short story 'A Martian Odyssey" (which has been anthologized a lot), wrote about a Martian creature that was silicon-based. It prodfuced waste silicon dioxide, which, as noted above, is a solid. It solved this problem by excreting it, building a sort of pyramid around itself. It moved when the pile of rock got too big to comfortably add to it. They found this thing at the end of a whole line of pyramids, increasing gradually in size, that was incredibly old. Weinbaum wrote this in the 1930s, and I’ll bet he wasn’t the first to consider the problem of silicon-based life.
Rock is only solid at temperatures comfortable for Earthlife - what about the idea of lava as the primordial soup?
Tne problem is that all that energy tends to break down molecular bonds. I won’t say it can’t ahppne, just that its going to have to have some method of dumping a lot of external heat.
Now I’m wondering about the elements below silicon! If there can be a silicon world, then how about a germanium world, an Sn world (which I don’t know what this element is maybe selenium?), a lead world, and an ununquadium world! I suppose they all must have four bonds directed to those corners of a tetrahedron.
Sn stands for tin, which, as a metal, doesn’t have the same bonding properties as the nonmetal carbon. For one thing, it has two common ions, only one of which forms four bonds (the other forms two). Also, as much as silicon forms weaker bonds than carbon, each element below it forms weaker and weaker bonds because there are more electrons between the valence (outer) electrons and the positive nucleus (this is known as the shielding effect).
CalMeacham, you beat me to it!
"Kirk and Spock encounter a Horta, the creature responsible for the deaths. Kirk and Spock fire phasers at it, but it gets away. Spock does a mind meld, and finds out the “alien monster” is actually a mother protecting its young.
An agreement is worked in which the creature will work with the miners, boring holes in solid rock for them. In return the creature’s children, silicon spheres, will be left alone."
Here’s my pitiful cite, you can google for a gazillion others:
Asimov discussed the various bases for life several times in his F&SF essays, showing what kinds of chemistry and biology various types of life would require.
This page on Asimov’s chemistry essays lists a few possibilities, including:
He did a number of essays on silicon in 1982 according to that listing.
IIRC Silicon, (because of its larger size?), has a lower tendency to form double and triple bonds than does carbon - Silanes are common, but something like Si2H4 or Si2H2 is much rarer. I imagine this could impact the chemistry of life.
I asked my chemistry prof this about 10 years ago and he said that whilst the Si-Si bond was too weak to be of any use, the addition of oxygen -Si-O-Si- made the bond strength much closer to carbon. Still difficult to form double bonds though.
Carbon’s actually got two things going for it: It can form long chains, and it can form complex molecular structures. Silicon can form the long chains (in asbestos, for instance), but it’s too clumsy for the intricate structures. There are also some other elements which can form intricate structures (nitrogen, phosphorus, beryllium), but they can’t do the long chain thing. So you’d need a lot to replace carbon, and carbon is a pretty abundant element anyway, so why bother?
Found it. It’s an Asimov story:
“The Talking Stone”
Dr. Wendell Urth once again comes to the rescue, helping Larry Vernadsky solve the mystery of the last words of a rock-eating silicon life form among the asteroids.
ASIMOV STORY [A.101]
PARTIAL PUBLICATION RECORD:
----- First publication: The Magazine of Fantasy and Science Fiction (October 1955)
----- Asimov’s Mysteries (1968)
----- The Complete Stories, Volume 2 (1992)