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Author Topic: Is the Periodic Table complete?  (Read 15724 times)

Offline time-cop

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Is the Periodic Table complete?
« on: 14/05/2012 01:26:00 »
I have (for once ) a sensible question, when was the Periodic Table first compiled, and have we filled all the gaps yet, or are there more elements to be discovered ?
« Last Edit: 14/05/2012 03:41:50 by Geezer »


 

Offline Geezer

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Re: Periodic Table
« Reply #1 on: 14/05/2012 03:39:44 »
I think we need to move it to the sensible questions place :)
 

Offline CliffordK

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Re: Is the Periodic Table complete?
« Reply #2 on: 14/05/2012 04:20:22 »
I think we can say that the periodic table is likely complete for stable elements (on earth?).

http://en.wikipedia.org/wiki/Periodic_table_(large_version)

There are a number of synthetic elements that have been produced that have a half-life of less than an hour, and it is likely that additional heavy elements will be synthesized in the future, but likely they will have short half-lives.

Several more hypothetical elements are included on an extended form of the periodic table.

http://en.wikipedia.org/wiki/Extended_periodic_table

Is it possible that Neutron Stars and Black Holes will contain additional elements, or perhaps some short half-life elements created in supernovas?

Anti-Elements are not included on the Periodic table, but I assume that people believe that they would have similar properties to the normal elements.  I believe both anti-hydrogen, and anti-helium have been produced.  Perhaps an anti-Lithium would be easier to contain if it could be synthesized. 
 

Offline damocles

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Re: Is the Periodic Table complete?
« Reply #3 on: 14/05/2012 21:46:13 »
Meanwhile, to the other part of the question. The first periodic tables were published in 1869, independently by the Russian scientist Dmitri Mendeleev and the German scientist Lothar Meyer. Both Mendeleev and Meyer had published earlier tables in 1864 that were clearly leading up to a periodic classification of elements.

Mendeleev published an improved version in 1871 that included many more elements, and he made some famous predictions about missing elements -- three of the elements were discovered in the next 15 years, and they had properties remarkably similar to those Mendeleev had predicted.

The first periodic tables built on work by English chemists Newland and Odling, and German Doebereiner.
 

Offline evan_au

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Re: Is the Periodic Table complete?
« Reply #4 on: 02/06/2012 10:50:27 »
In a sense, a neutron star is the nucleus of one big atom with a very high atomic number.
A neutron star may have an "ocean" or "atmosphere" formed from nuclei from exotic elements.
 

Offline Guthers

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Re: Is the Periodic Table complete?
« Reply #5 on: 02/06/2012 19:57:13 »
There aren't any gaps in the periodic table, but in theory you could have more and more elements at the top end, in extreme conditions and perhaps for very short times.

And a neutron star, by definition, doesn't have any protons as they have all been converted to neutrons, so can't be considered an atomic nucleus. The atomic number is the number of protons in the nucleus.
 

Offline damocles

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Re: Is the Periodic Table complete?
« Reply #6 on: 03/06/2012 03:11:59 »
There aren't any gaps in the periodic table, but in theory you could have more and more elements at the top end, in extreme conditions and perhaps for very short times.

And a neutron star, by definition, doesn't have any protons as they have all been converted to neutrons, so can't be considered an atomic nucleus. The atomic number is the number of protons in the nucleus.

I am afraid that that is not strictly true Guthers. A neutron star contains huge numbers of neutrons, but the high temperature and the second law of thermodynamics mandates that many (numerically, not proportionally) of the neutrons will be transformed into protons and electrons, in which case the neutron star IS an atomic nucleus, with an atomic number that is continually changing within a small range because of the statistics of dynamic neutron-proton transformations.
 

Offline Guthers

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Re: Is the Periodic Table complete?
« Reply #7 on: 04/06/2012 17:43:24 »
While there is a model which allows for some protons to exist in a neutron star, it is not at all accurate to describe such an object as an atomic nucleus.
 

Offline Bored chemist

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Re: Is the Periodic Table complete?
« Reply #8 on: 04/06/2012 17:45:52 »
Why not?
 

Offline CliffordK

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Re: Is the Periodic Table complete?
« Reply #9 on: 05/06/2012 00:12:36 »
Wikipedia has a good description of Neutron stars.

Proceeding inward, one encounters nuclei with ever increasing numbers of neutrons; such nuclei would decay quickly on Earth, but are kept stable by tremendous pressures.

Proceeding deeper, one comes to a point called neutron drip where neutrons leak out of nuclei and become free neutrons. In this region, there are nuclei, free electrons, and free neutrons. The nuclei become smaller and smaller until the core is reached, by definition the point where they disappear altogether.


Of course, most of this has not been directly observed so it is all generally hypothetical.

Anyway, it would not be a homogeneous structure throughout the star.  The wikipedia article discuses strong and weak interactions.  Presumably an energy transition has to occur for fusion to occur, either absorbing energy for a large atom, or releasing energy for a small atom.
 

Offline Guthers

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Re: Is the Periodic Table complete?
« Reply #10 on: 05/06/2012 19:52:11 »
Why not?
Perhaps if you were a bored physicist you would know  ;)
 

Offline Lab Rat

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Re: Is the Periodic Table complete?
« Reply #11 on: 07/10/2012 18:40:20 »
I have (for once ) a sensible question, when was the Periodic Table first compiled, and have we filled all the gaps yet, or are there more elements to be discovered ?
Theoretically and ideally, the periodic table could be infinitely big.  However, I assume that the farther you go on this infintely big periodic table, the more incredibly unstable the elements would be-maybe even being detectable for far less than milliseconds.  Also, assuming that the next element in Group 1 had the same characteristics as all the other elements except for hydrogen, it would be incredibly explosive in water (look up francium in water videos on youtube).
 

Offline damocles

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Re: Is the Periodic Table complete?
« Reply #12 on: 07/10/2012 22:16:06 »
I have (for once ) a sensible question, when was the Periodic Table first compiled, and have we filled all the gaps yet, or are there more elements to be discovered ?
Theoretically and ideally, the periodic table could be infinitely big.  However, I assume that the farther you go on this infintely big periodic table, the more incredibly unstable the elements would be-maybe even being detectable for far less than milliseconds.  Also, assuming that the next element in Group 1 had the same characteristics as all the other elements except for hydrogen, it would be incredibly explosive in water (look up francium in water videos on youtube).

If there are "francium in water" videos on youtube, they are a big con! Francium is a very unstable element with very dangerous radiations. Its longest lived isotope has a half-life of 22 minutes. It has never been produced or isolated in bulk, and certainly not as a pure metal that would react with water
 

Offline Lab Rat

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Re: Is the Periodic Table complete?
« Reply #13 on: 08/10/2012 15:18:33 »
Thanks for the information.
There was only one or two videos.  One was an old black and white video that was supposedly the U.S. army dumping francium into the ocean.  From what I remember, it showed a truck backing up to the edge of a cliff.  A very short time later, a mushroom type cloud came up from the water.  I thought that it could be real with the way that the army tested atomic bombs, etc. in the desert and in the ocean during WWII and the Cold War, but now I guess I know it isn't real.
Thanks again. :)
« Last Edit: 08/10/2012 15:20:38 by Lab Rat »
 

Offline evan_au

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Re: Is the Periodic Table complete?
« Reply #14 on: 14/10/2012 05:39:58 »
For some time, physicists have hypothesised that a group of elements near 115 may be more stable than those slightly lighter and those slightly heavier: http://en.wikipedia.org/wiki/Island_of_stability

The reason for this hypothesis is that atoms with their protons & neutrons filling a complete shell tend to be more stable. These are nicknamed "magic numbers"; note that different theories predict different values for the number of nucleons in each shell.
However, it is hard for a collider to create a nucleus in the expected ranges, because the potential infeed atoms don't have enough neutrons.
« Last Edit: 14/10/2012 05:43:33 by evan_au »
 

Offline Virginia J. Pina

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Re: Is the Periodic Table complete?
« Reply #15 on: 17/04/2014 14:27:38 »
Have a great discussion, Topic is much interesting. :-X I think periodic table is almost complete although there should be more elements.  :D
 

Offline Bored chemist

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Re: Is the Periodic Table complete?
« Reply #16 on: 17/04/2014 16:20:09 »
This is a very old thread.
Here's the video that LabRat referred to.
It makes rather more sense when you see it's not about francium, but sodium.

 

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Re: Is the Periodic Table complete?
« Reply #16 on: 17/04/2014 16:20:09 »

 

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