[ukmicky (OP)]

How much is missing from the periodic table,How high can it go, is there a limit.

Are superheavy elements like ununquadium unbinilium and unbihexium real and what properties could these or other new elements have.

[David Sparkman]

All of the super heavy elements discovered in the last 50-60 years have extrememly short half lives (read highly radioactive), and are very hard to discribe as we can't make much of it, much less experiment with them as they exist for only a fraction of a second.

Is there a stable higher order element? Probabiliy not, but if it were, it would be very expensive, and have mediorce properties.

That the higer order atoms are so highly unstable may be due to the size of the nucelous exceding size of the field of the force that holds the center of the atom together.

David

[gerard]

its theorised thought that there is a plateau of stability somewhere around the 250 mark i think.

[Simmer]

I remember reading the same thing but it begs the question, if these elements are stable why haven't we found some?

[rosy]

Well, I know nothing at all here so I'm guessing but if these Z=250 type elements are to be formed it would have to be by fusion of smaller nuclei which would probably themselves be unstable... so it's possible I guess that they just don't form in lab conditions/elsewhere in detectable amounts because there has to be a collision between two very short-lived species for them to be formed at all. Also, "stable" may mean "more stable than the high-Z unstable stuff we've already made" rather than stable in the sense of C-12.

[Simmer]

Makes sense, or maybe it's just that we don't recognise the h-orbital transitions in stellar spectra :-)

[Ylide]

In general, you can think of it as a tendency for larger elements to have the repulsive force of the protons in the nucleus start to become stronger than the attractive nuclear force that holds them together.  Islands of stability come from the ratio of neutrons to protons (i.e. added nuclear force from neutrons) being favorable towards nuclear force holding the nucleus together.  Once you reach a certain nucleus size, the nuclear force becomes less and less able to overcome the repulsive force of the protons.  I'm told the actual structure, that is relative positions of neutrons to protons, is a factor but I couldn't begin to explain how.

This message brought to you by The Council of People Who Are Sick of Seeing More People

[Simmer]

Nuclear structure being the arrangement of neutrons and protons that minimises repulsive forces, I take it?  I suppose that's where the islands of stabiity idea comes from - I wonder if technetium is an island of instability for the same reason?