Helium is unreactive, because it has two electrons in a shell that holds two electrons. It doesn’t want any more, and doesn’t want to lose any.
Well, stuff that! There could (and should) be a physical state where it shares those electrons with another atom. On checking the web, it turns out that in plasma conditions it can exist (excimer), though it isn’t much use in ordinary everyday life.
OK, so helium can be forced eventually to play, even if not especially nicely. What about carbon? Carbon has 4 electrons in its outer shell and wants 8 so is happy to form 4 covalent bonds with other atoms. So it is much nicer to play with than helium. However…..
Suppose, just suppose, that having shared its outer electrons, we can do some sort of sub-chemistry with its inner ones. OK, I know that isn’t quite the norm. What sort of thing would we have to do to make atoms engage in some sort of super-chemistry with their inner electron shells? Stupid question, possibly, but I am a futurologist, not a historian, (or a chemist) and know that old barriers don’t always last.
The reason I am interested in is that I am brainstorming new kinds of carbon materials, just for fun. We already have several allotropes with some great and useful properties. Diamond is quite strong, graphene is stronger, but a bit thin, so wouldn’t it be nice to have a 3D material like diamond but which has better bonds? I was drawing some pretty pics of graphene and noticed an optical illusion appearing, where it starts to look cubic, except that some of the lines are missing. Each point in a cubic array has 6 links, or bonds, not 4. Diamond has 4 , but if a super-diamond had 6, it might be better still.
So, we can get 4 carbon bonds with the outer electrons easily enough, but IF we could somehow get the two inner ones to play in some sort of virtual excimer as well … what should happen is that we could make a cubic form of carbon. Which, idly speculating, should exist as a sort of solid plasma. At very high temperatures, far beyond what diamond could cope with. Being able to withstand high forces at high temperatures, and conducting electricity, it would be possible to build one hell of a plasma rifle with it. Or an electron pipe that could carry a billion times higher data rates than optical fibre. http://thisshouldbeok.wordpress.com/2011/04/09/electron-pipe/
We can’t do it yet, but just for the record, you saw it here first.