2006-06-13 01:59:25 · 22 answers · asked by itsme 3 in Science & Mathematics ➔ Other - Science
That'd be Astatine, there's about 25g of naturally occurring Astatine on the planet only.
2006-06-13 02:03:46 · answer #1 · answered by flammable 5 · 3⤊ 0⤋
If we are talking about what occurs in nature ...
Anti-matter would be one answer, And thus anti-astatine would seem likely to be the most rare form of anti-matter.
But no Transuranic element (atomic weight of > 92) especially where all its isotopes have very short half-lives occurs in nature (and so there are a choice of twenty or more of these) would be another
Bose-Einstein condensate (which only exists at nano-Kelvins above Absolute Zero) would be a third
Nano-tubes, nanofoam and Buckyball (three allotropes of Carbon) would be a fourth
A quark that is not contained in a hadron woild be a fifth.
Microbes from Mars would be a sixth and molecules of Titan's atmosphere would be a seventh
And as regards astatine, we should look for the isotope of Astatine with the shortest half-life
http://en.wikipedia.org/wiki/Isotopes_of_astatine
which turns out to be At-213 with a half-life of 125 nanoseconds (85 protons 128 neutrons)
There are in fact no stable isotopes of astatine. The 30gms mentioned is in the earth's crust and what it should really say is that there are no more than 30 gms at any one time of astatine, as all its isotopes are part of the decay chains of uranium and thorium, and once created as a result of fissile reactions the half-lives of astatine isotopes are so short (a few hours at most) that the world stocks of astatine are both constantly dwindling and constantly being replenished at one and the same time.
When Astatine-211 decays, it does so to Polonium-211 and thence to a stable isotope of lead, Pb-207.
Other answers might include
an honest politician
the milk of human kindness
a fair trial
2006-06-13 02:37:17 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Element 85 on the periodic table : Astatine
DALE R. CORSON, CORNELL UNIVERSITY appeared in the "Guinness Book of World Records" for having discovered the rarest substance on Earth.
2006-06-13 02:05:56 · answer #3 · answered by sally T 2 · 0⤊ 0⤋
Since u mentioned "Substance" and "Rarest",
then it would be "Anti-matter".
It is a substance if collected in enough amount, will create the puriest energy more cleaner than nuclear energy. Gram for gram it is more powerful and efficient than any nuclear substance. Also there are no dangers of radiation unlike nuclear.
1 gram of Anti-matter is valued for more than US$5000.
2006-06-13 04:13:16 · answer #4 · answered by gdfella2 2 · 0⤊ 0⤋
the rarest substance is ME
2006-06-13 02:03:20 · answer #5 · answered by mc_1_2000 3 · 0⤊ 0⤋
Wisdom
2006-06-13 02:02:59 · answer #6 · answered by sincityq 5 · 0⤊ 0⤋
Loyalty!
2006-06-13 02:03:12 · answer #7 · answered by Iron Rider 6 · 0⤊ 0⤋
Common sense.
2006-06-13 02:03:07 · answer #8 · answered by Alan L 2 · 0⤊ 0⤋
Platinum?
2006-06-13 02:02:29 · answer #9 · answered by squimberley 4 · 0⤊ 0⤋
ASTATINE only 30g of it on the whole of earth
2006-06-13 02:04:33 · answer #10 · answered by ptdemon 3 · 0⤊ 0⤋