## Infinite number of elements?

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alphawolf29
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### Infinite number of elements?

someone asked my friend and myself how many elements there were, my friend said "Around one hundred eight" And i said "Infinite" We cant really decide who was right (Not one hundred and eight, but whether there is an infinite number or not) My argument is that, as long as you can keep sufficient pressure and heat, you can pump as many protons into hydrogen as you like, stable or not. My education only goes as far as chemistry 12, so i havent the slightest clue.

In summary, could there be an infinite number of elements?

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### Re: Infinite number of elements?

Presumably, there is an upper limit, since the heat would break the protons or nucleas eventually*.

*I have little-to-no education in nuclear physics. Ignore me if someone comes up with a better answer.
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alphawolf29
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### Re: Infinite number of elements?

Wouldnt the increase in pressure mean more energy would be need to break it apart? and therefore always increasing the upper limit...and infinity

andyisagod
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### Re: Infinite number of elements?

http://www.newton.dep.anl.gov/askasci/phy05/phy05174.htm is actually a nice answer to the question. I would say that the number of elements really isn't infinite I mean theoretically you could name an element with any atomic number you want but in practice it might not be stable or even bound at all. Another problem would be you are limited to the number of protons in the universe .

BlackSails
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### Re: Infinite number of elements?

You can only add nucleons until you have enough mass to collapse into a black hole. So there is a finite number of elements.

There are a much smaller finite number of stable elements though. There is reason to believe there is another cluster started around 120ish(?), but that may or may not exist.

Kow
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### Re: Infinite number of elements?

BlackSails wrote:There is reason to believe there is another cluster started around 120ish(?), but that may or may not exist.

Explain.

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### Re: Infinite number of elements?

Kow wrote:
BlackSails wrote:There is reason to believe there is another cluster started around 120ish(?), but that may or may not exist.

Explain.

Wikipedia has a reasoanble deal to say on the subject.
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### Re: Infinite number of elements?

Oh, that's just begging for scifi (syfy, sorry) stories to be written about the synthesis of these elements, which would of course have Amazing Properties (tm).
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Luthen
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### Re: Infinite number of elements?

I'm sure it's been done.

I'm not sure this is evenly remotely possible, but what would happen when you have so many nucleons that the nucleus's diameter is wider than the range of the Strong Force?
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Soralin
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### Re: Infinite number of elements?

There's always neutron stars for really big atomic nuclei, or something similar to it.

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### Re: Infinite number of elements?

Soralin wrote:There's always neutron stars for really big atomic nuclei, or something similar to it.

Ah yes, my favorite isotope. [imath]^{1000000000000000000000000000000000000000000000000000000000}Ns[/imath]
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Luthen
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### Re: Infinite number of elements?

Yep, I've made a fool of myself for the next month. It had to happen sooner or later.
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BlackSails
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### Re: Infinite number of elements?

Kow wrote:
BlackSails wrote:There is reason to believe there is another cluster started around 120ish(?), but that may or may not exist.

Explain.

Yeah, the island of stability, as mentioned above, has some theoretical justification.

By far the strangest (hah) nuclei are the hypernuclei. http://en.wikipedia.org/wiki/Hypernucleus

Avian
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### Re: Infinite number of elements?

Luthen wrote:I'm not sure this is evenly remotely possible, but what would happen when you have so many nucleons that the nucleus's diameter is wider than the range of the Strong Force?

If I remember correctly the fact that binding energy per nucleon starts to drop after iron is the consequence of the nucleus growing larger than the range of the strong force.

The fact that heavier elements are unstable is exactly because strong force can't hold the nucleus together against the elecromagnetic repulsion.

Minerva
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### Re: Infinite number of elements?

It's likely that the highest atomic number of a nucleus which can exist in anything like a conventional atom is Z = 138.

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

In any case, yes, as someone mentioned above, hypernuclei are extremely cool
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Certhas
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### Re: Infinite number of elements?

I would argue that a neutron star is not an atom because it is gravitationally bound and not strong force bound. Also the point of an atom is that it is stable in vacuum, not just under pressure. Otherwise you'd eventually end up with some sort of quark-gluon plasma I guess.

If I would translate the question into a more precise one I would formulate it like this: Are there metastable bound states of protons+neutrons under the strong+weak+EM force with arbitrarily high mass?

My intuition is that this is not the case. After all most combinations of protons+neutrons don't even exist as metastable states. The electromagnetic interaction and or thermodynamic instability simply washes out the strong force potential.

But I am not a nuclear physicists.
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### Re: Infinite number of elements?

Certhas wrote:I would argue that a neutron star is not an atom because it is gravitationally bound and not strong force bound. Also the point of an atom is that it is stable in vacuum, not just under pressure.

A neutron star is stable in a vacuum. What do you think space is, if not a vacuum? And i don't really see why gravitationally bound would not count.

So yeah, I think a neutron star counts as a single nucleus.

(Actually that is not entirely true. Only the inside of a neutron star would be a single nucleus. There is more ordinary matter near the edge).

Anyway the mass of neutron stars has an upper bound. Somewhere between 2 and 4 solar masses.
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Rentsy
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### Re: Infinite number of elements?

No. A Neutron star is not an atom. An atom is a positively charged group of positive and neutral particles, orbited by negatively charged particles. Those negatively charged particles interact with the negatively charged particles of other atoms, in what are commonly termed "chemical reactions".

An atom needs to be capable of electrical interactions with other atoms.

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### Re: Infinite number of elements?

We're all forgetting Jumbonium.
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BlackSails
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### Re: Infinite number of elements?

Minerva wrote:It's likely that the highest atomic number of a nucleus which can exist in anything like a conventional atom is Z = 138.

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

In any case, yes, as someone mentioned above, hypernuclei are extremely cool

Apart from it not really meaning all that much to ask what the velocity of an electron in orbit around a nucleus is, the entire idea of orbitals starts to fall apart at such high atomic numbers.

Edit: Also, the stability of the electron orbitals doesnt impact the stability of the nucleus

Certhas
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### Re: Infinite number of elements?

Certhas wrote:I would argue that a neutron star is not an atom because it is gravitationally bound and not strong force bound. Also the point of an atom is that it is stable in vacuum, not just under pressure.

A neutron star is stable in a vacuum. What do you think space is, if not a vacuum? And i don't really see why gravitationally bound would not count.

So yeah, I think a neutron star counts as a single nucleus.

That should have been two paragraphs. As in: "You can't add more and more by increasing the pressure." and "Neutron stars are gravitationally bound".

Well you can call it a nucleus if you want. Fact is that its a physically very very different system. I think the question asked by the OP becomes much more interesting if you parse it as I did. It certainly has no relationship with the nucleus of an atom as the latter is usually understood, other than that it is made from neutrons which also happen to be part of the makeup of atomic nuclei.
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oxoiron
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### Re: Infinite number of elements?

Rentsy wrote:An atom is a positively charged group of positive and neutral particles, orbited by negatively charged particles.
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### Re: Infinite number of elements?

Sir_Elderberry wrote:Oh, that's just begging for scifi (syfy, sorry) stories to be written about the synthesis of these elements, which would of course have Amazing Properties (tm).

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BlackSails
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### Re: Infinite number of elements?

oxoiron wrote:
Rentsy wrote:An atom is a positively charged group of positive and neutral particles, orbited by negatively charged particles.

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### Re: Infinite number of elements?

Ok then, what about tetraneutrons? (if their existence is confirmed by more evidence)
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Cryopyre
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### Re: Infinite number of elements?

You can also have really bad ass super-atoms. Gold can be bound together in such a way that it becomes a halogen.
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BlackSails
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### Re: Infinite number of elements?

Meteorswarm wrote:
Cryopyre wrote:You can also have really bad ass super-atoms. Gold can be bound together in such a way that it becomes a halogen.

Explain? The chemical properties of an atom are dependent on its electrons, which in turn are dependent on the number of protons it has. I fail to see how rearranging the nucleus can change this.

No its true. Small clusters of atoms can have wildly different properties from the atoms themselves. Spectroscopic studies of Al(13)I- shows that the electron spends most of its time on the aluminum cluster, showing that the Al(13) is more electronegative than the iodine!

Certhas
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### Re: Infinite number of elements?

Plasma Man wrote:Ok then, what about tetraneutrons? (if their existence is confirmed by more evidence)

I'd submit the definition strongly bound baryons again. All the core physics of nuclei flows from these facts. The rest is sort of incidental as far as nuclear physics is concerned. That would also include nuclei made from Baryons with strange, charm, top or bottom quarks.
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