What is the molecular composition of unobtanium?

If it's unobtainable, we will never know.

The Nobel Prize in Chemistry this year related to the discovery of a
small protein called ubiquitin, important to the biology of protein
modification and degradation.

For a brief discussion of its molecular composition see here:

[The Ubiquitin System]
http://homepages.bw.edu/~mbumbuli/cell/ublec/

High-order entries in the periodic table whose "discovery" has not
been confirmed are named according to their atomic number.  Thus the
unconfirmed element with atomic weight 118 (which was the subject of a
now-retracted research paper back in 1999) is often called ununoctium
(1-1-8).  Of course there can be little question of the "molecular
composition" of a chemical element.

[The Element Ununoctium]
http://education.jlab.org/itselemental/ele118.html

regards, mathtalk-ga

Unobtainium is the make believe material that has whatever properties
you need it to. Its a standard scientific / engineering joke.

Wikipedia has a nice article at http://en.wikipedia.org/wiki/Unobtanium.  

I am assuming milomar ~knew~ of unobtainium's roots in science fiction
and was actually asking if anyone knows if any of the science fiction
sources that refer to unobtainium ever revealed its molecular
composition.  I have not heard or read of any such additional
exposition, but will keep looking.

I suspect that the imaginary element unobtainium is classifed as one
of the 'heavy mentals'. It certainly isn't a no-bull gas.