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Author Topic: Which radioactive elements have the longest and shortest half lives?  (Read 83878 times)

Offline Quantum_Vaccuum

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What elements have the longest, or the shortest half life?
« Last Edit: 09/05/2008 22:27:44 by chris »


 

Offline Quantum_Vaccuum

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nvm problm solved: I finally found the element with longest half life, as stated in my element book," Uranium is the last and heaviest of the natural elements" (203). "its half-life of 4.6 billion years makes it the longest-lived of all isotopes. A long half-life means that an isotope is less active, and that fewer of tis atomic nuclei disintegrate in any given period. Uranium-235 has a half-life of 700 million years, while uranium-234 has a half-life of only 25 million years" (203).

Therefore i was correct, and Uranium does have the largest half life, but not uranium-235 as I suspected t first.
 

Offline DoctorBeaver

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Here are a few others


Strontium-90 - 28 years
Caesium-137 - 30 years
Plutonium-239 - 24,000 years
Caesium-135 - 2.3 million years
Iodine-129 - 15.7 million years

I'm trying to find the 1 with the shortest half life. Wouldn't it be 1 of the trans-uranic elements?
 

Offline lightarrow

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What elements have the longest, or the shortest half life?
(What I think is) the longest: Hydrogen 1H > 1030 years
The shortest I've found: Darmstadtium 267Ds = 3*10-6 seconds
 

Offline Quantum_Vaccuum

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I read in my element book that Uranium is the longest, and wouldn't one of the man-made elements like Uuq be the shortest life elelment?
 

Offline lightarrow

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I read in my element book that Uranium is the longest, and wouldn't one of the man-made elements like Uuq be the shortest life elelment?
About the shortest half life, you should be right, since wikipedia says, about UUq isotopes:
Quote
So far, all three that have been made have undergone spontaneous fission in the first .0012 milliseconds
That corresponds to 1.2*10-6 seconds.

About the longest half life, in your first post you asked:
Quote
What elements have the longest, or the shortest half life?
You didn't write: "..among radioactive elements"
 

Offline Quantum_Vaccuum

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i know, uranium still has the most overall, according to my book, but that may be a bit out of date.
 

Offline lightarrow

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i know, uranium still has the most overall, according to my book, but that may be a bit out of date.
Your book will certainly report the stability of radioactive isotopes, not of every isotope; the non-radioactives are considered as stable, but it's not completelly true, since even a proton is expected to decay (after more than 1030 years, however!)
 

Offline Bored chemist

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http://physicsworld.com/cws/article/news/17319
 Also one of the vanadium isotopes has a half life of about 10^17 years so uranium's nowhere near the longest.
 

Offline DoctorBeaver

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i know, uranium still has the most overall, according to my book, but that may be a bit out of date.
Your book will certainly report the stability of radioactive isotopes, not of every isotope; the non-radioactives are considered as stable, but it's not completelly true, since even a proton is expected to decay (after more than 1030 years, however!)

Hang on... isn't that true only according to Georgi & Glashow's Unified Theory? And even then, they arrived at their conclusion by extrapolating to energy levels thousands of times greater than we can currently manage.
 

Offline lightarrow

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i know, uranium still has the most overall, according to my book, but that may be a bit out of date.
Your book will certainly report the stability of radioactive isotopes, not of every isotope; the non-radioactives are considered as stable, but it's not completelly true, since even a proton is expected to decay (after more than 1030 years, however!)

Hang on... isn't that true only according to Georgi & Glashow's Unified Theory?
Yes; an entire class of GUTs, however, not only one of them:
http://en.wikipedia.org/wiki/Proton_decay

Quote
And even then, they arrived at their conclusion by extrapolating to energy levels thousands of times greater than we can currently manage.
Yes.
 

Offline Bored chemist

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If we are talking about experimentally verified decay processes I thing 209Bi wins. If we are talking about theoretical matters the I think the administratium* nucleus has the longest half life. It has to outlive the proton to make sure that the proton decay is properly documented and thet the apropriate bills are sent out.

*
http://en.wikipedia.org/wiki/Administratium
 

Offline Dehoqu

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128Te has the longest known half-life, 2.2×1024 years (approx. 2.2 sextillion years)
 

Offline Bored chemist

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That must have been tricky to measure- it's getting "close"* to the predicted half life for the proton.

* "close" in this context means within a factor of a million or so.
 

Offline ScienceFreak01

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Copernicium 285 has the shortest half life, which is 5*10^-19 seconds. Longest is definitely uranium 238, over a billion years.
 

Offline Geezer

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I wonder what the half life of this thread is.
 

Offline Bored chemist

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I wonder what the half life of this thread is.
Apparently not long enough for Science Freak 01 to read it and find out that there are lots of things with much longer half lives than uranium.
 

Offline damocles

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Given that the original question was about ELEMENT and not ISOTOPE, then thorium, element 90.  lasts about 3 times longer than uranium, element 92.
It would have some claim. There would be no excuse for a textbook published at any time in the 20th century to cite uranium as the longest lived natural element; Thorium is 3 times more abundant in the Earth's crust, and 3 times longer-lived.

It has recently (2006) been found that the "stable" isotope of bismuth, element 83, isotope 209, is actually radioactive, with a half life greater than 10^19 years.
Bismuth is probably the best answer in terms of present knowledge and understandings. Check out http://en.wikipedia.org/wiki/Isotopes_of_bismuth

IF the proton itself is unstable (and that is far from universally accepted, then I would suspect that every other nucleus with the possible exception of Helium-4 is also unstable as a consequence, but I do not know that this is the case. Perhaps a physicist well-versed on this theory could help us out here.

Which element has the shortest half-life is really an undecidable question. It boils down to the question of at what point will scientists accept that a new element has actually been created, and at what point will they prefer other explanations of phenomena occurring over minute time intervals. There is no natural criterion.
 

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