Elements

[SuperFastJellyfish]

How many elements can exist, or maybe, what ranges of atomic numbers should be able to stably exist?  I've googled it, and read that a neutron star can be considered an enormous nucleus.  That makes for a gap somewhere between atomic numbers 118 and 3x10^59(give or take a few orders of magnitude).  What are the constraints within this gap?

[lajoswinkler]

Neutron star is not considered to be an enormous nucleus. That's just a curious analogy. It's being held by gravity, not strong nuclear force, and it has WAY more neutrons than protons. Also, in its depth, it probably has quark-gluon plasma.

Here.

Edited March 16, 2016 by lajoswinkler

[Darnok]

4 hours ago, SuperFastJellyfish said:

How many elements can exist, or maybe, what ranges of atomic numbers should be able to stably exist?  I've googled it, and read that a neutron star can be considered an enormous nucleus.  That makes for a gap somewhere between atomic numbers 118 and 3x10^59(give or take a few orders of magnitude).  What are the constraints within this gap?

Black hole is last "element".

But remember that elements are our creation only, they are like sections/paragraphs of matter, while matter itself is continuous.

[lajoswinkler]

57 minutes ago, Darnok said:

Black hole is last "element".

But remember that elements are our creation only, they are like sections/paragraphs of matter, while matter itself is continuous.

Elements are not our creation of mind. They are not arbitrary. Each element is defined by the number of protons in its nucleus. That's it. If it has two of them, it's helium and it will have specific chemical properties arising from the two electrons that are neutralizing its atom. Nobody can change that.

[Atlas2342]

58 minutes ago, Darnok said:

Black hole is last "element".

I dont think black holes are elements. I think they're phenomena

[cantab]

On Earth the highest element found naturally in significant abundance is Uranium, atomic number 92.

The mainstream view is that isotopes in the "island of stability" might have half lives of milliseconds or seconds, rather than microseconds or nanoseconds. There's a minority view that they could be stable over "human timescales" - hours, days, maybe even a few years. But I don't think anyone seriously reckons they could be stable over geological timescales.

The problem I see, if these elements are stable over even hours, why have we not seen them in spectra of supernovae? In our labs on Earth superheavy elements are hard to make because it's hard to get enough neutrons, because the higher the atomic number the higher the neutron:proton ratio so adding two stable light elements doesn't give the most stable isotope of a superheavy. But supernovae - some of them at least - are very neutron-rich environments, I'm thinking it ought not to be a problem.

Ignoring radioactive instability, various figures have been given for the "end of the periodic table", but the most current one is around atomic number 173. Beyond that the electron orbitals around the nucleus misbehave and it's thought that even if the nucleus was stable, it could not form a neutral atom.

[peadar1987]

4 hours ago, lajoswinkler said:

Elements are not our creation of mind. They are not arbitrary. Each element is defined by the number of protons in its nucleus. That's it. If it has two of them, it's helium and it will have specific chemical properties arising from the two electrons that are neutralizing its atom. Nobody can change that.

I would not be entirely surprised to discover that Darnok does not subscribe to atomic theory.

[sevenperforce]

5 hours ago, Darnok said:

Black hole is last "element".

But remember that elements are our creation only, they are like sections/paragraphs of matter, while matter itself is continuous.

This is bullocks.

4 hours ago, Atlas2342 said:

I dont think black holes are elements. I think they're phenomena

I suppose everything is a "phenomenon" in some sense. But black holes are merely very dense heavy objects which happen to have fallen afoul of the curvature of spacetime. 

1 hour ago, cantab said:

On Earth the highest element found naturally in significant abundance is Uranium, atomic number 92.

The problem I see, if these elements are stable over even hours, why have we not seen them in spectra of supernovae? In our labs on Earth superheavy elements are hard to make because it's hard to get enough neutrons, because the higher the atomic number the higher the neutron:proton ratio so adding two stable light elements doesn't give the most stable isotope of a superheavy. But supernovae - some of them at least - are very neutron-rich environments, I'm thinking it ought not to be a problem.

Supernovae may not get hot enough to synthesize the really heavy stuff. There's a fair chance that gold and heavier elements come not from supernovae, but from neutron star collisions. 

[cantab]

Well a neutron star collision is an even more neutron-rich event. Anyway I still find it hard to imagine that these kinds of highly-energetic natural phenomena would be unable to synthesise a stable superheavy element.

[sevenperforce]

16 minutes ago, cantab said:

Well a neutron star collision is an even more neutron-rich event. Anyway I still find it hard to imagine that these kinds of highly-energetic natural phenomena would be unable to synthesise a stable superheavy element.

Point being that we would not necessarily see them in the spectra of neutron star collisions because they are fairly rare events compared to supernovae.

[fredinno]

11 hours ago, lajoswinkler said:

Elements are not our creation of mind. They are not arbitrary. Each element is defined by the number of protons in its nucleus. That's it. If it has two of them, it's helium and it will have specific chemical properties arising from the two electrons that are neutralizing its atom. Nobody can change that.

What about Neutronium (element with 0 neutrons). Is that an element?

8 hours ago, cantab said:

On Earth the highest element found naturally in significant abundance is Uranium, atomic number 92.

The mainstream view is that isotopes in the "island of stability" might have half lives of milliseconds or seconds, rather than microseconds or nanoseconds. There's a minority view that they could be stable over "human timescales" - hours, days, maybe even a few years. But I don't think anyone seriously reckons they could be stable over geological timescales.

The problem I see, if these elements are stable over even hours, why have we not seen them in spectra of supernovae? In our labs on Earth superheavy elements are hard to make because it's hard to get enough neutrons, because the higher the atomic number the higher the neutron:proton ratio so adding two stable light elements doesn't give the most stable isotope of a superheavy. But supernovae - some of them at least - are very neutron-rich environments, I'm thinking it ought not to be a problem.

Ignoring radioactive instability, various figures have been given for the "end of the periodic table", but the most current one is around atomic number 173. Beyond that the electron orbitals around the nucleus misbehave and it's thought that even if the nucleus was stable, it could not form a neutral atom.

The island of stability elements likely aren't stable, or are made in such rare combinations (like nuclear isomers) that they won't show up at all.

1 hour ago, cantab said:

Well a neutron star collision is an even more neutron-rich event. Anyway I still find it hard to imagine that these kinds of highly-energetic natural phenomena would be unable to synthesise a stable superheavy element.

They can, these events are just very unlikely, and the superheavy elements would still decay very quickly. https://en.wikipedia.org/wiki/R-process

The R process produces mostly radioactive elements that decay back into Lead, Mercury and Platinum. However, the island of stability is far from the naturally produced elements, and likely isn't 100% stable anyways,(starting around 118-120, instead of the R process peaking around 90) so element formation will be rare indeed.

 

[cantab]

33 minutes ago, fredinno said:

What about Neutronium (element with 0 neutrons). Is that an element?

Personally I'm inclined to say no, not in the normal sense of "element", because it isn't involved in chemical processes.

[Tex]

2 hours ago, fredinno said:

What about Neutronium (element with 0 neutrons). Is that an element?

No, it's not, because elements are defined by protons only. Add as many electrons or neutrons as you want, it will still depend on the protons. It will just become an ion with a massive charge that wants to become neutral or a very unstable isotope that will eventually get rid of its own neutrons. The smallest possible element is Hydrogen with exactly 1 proton and 1 neutron electron.

[lajoswinkler]

55 minutes ago, fredinno said:

What about Neutronium (element with 0 neutrons). Is that an element?

You mean 0 protons? No, that's not an element. Chemical elements are made out of atoms. Element with Z=0 was just a funny curiosity back when people didn't really know what made up the atoms. Some very old periodic tables included it.

[sevenperforce]

30 minutes ago, Maximus97 said:

No, it's not, because elements are defined by protons only. Add as many electrons or neutrons as you want, it will still depend on the protons. It will just become an ion with a massive charge that wants to become neutral or a very unstable isotope that will eventually get rid of its own neutrons. The smallest possible element is Hydrogen with exactly 1 proton and 1 neutron.

Methinks you mean one proton and one electron. Hydrogen comes in three isotopes: protium, with one electron and one proton; deuterium, with one electron, one proton, and one neutron, and tritium, with one electron, one proton, and two neutrons. 

I suppose you can imagine a 1+ deuterium ion with just one proton and one neutron....

[Tex]

40 minutes ago, sevenperforce said:

Methinks you mean one proton and one electron.

Whoopsie, yes, that's what I meant. Edited.

[cantab]

Then there's stuff like muonium and positronium, both of which I believe have been observed forming molecules with both normal elements and themselves. (Short-lived molecules, but detectable nonetheless.) What do we consider them as? Elements in their own right? Exotic isotopes of hydrogen? Something else entirely?

[StrandedonEarth]

4 hours ago, fredinno said:

What about Neutronium (element with 0 neutrons). Is that an element?

"Neutronium" is generally used to describe the stuff that makes up a neutron star. Unimaginably dense stuff; simply pure neutrons, with none of the empty space you would 'see' between an atom's nucleus and its electron shell. It doesn't fit the definition of an element, but logically I would expect it should be considered an element in its own right. It would be just to the left of 'unobtainium'

[kerbiloid]

"Photonium" - a very common chemical element with 0 protons, 0 neutrons, 0 electrons.

[kerbiloid]

1 hour ago, p1t1o said:

-snip-

Why "nope"? It's the lightest element.

Edited March 17, 2016 by Maximus97
Contained reaction image only, which is not allowed.

[sevenperforce]

12 hours ago, cantab said:

Then there's stuff like muonium and positronium, both of which I believe have been observed forming molecules with both normal elements and themselves. (Short-lived molecules, but detectable nonetheless.) What do we consider them as? Elements in their own right? Exotic isotopes of hydrogen? Something else entirely?

Those are (exotic) atoms, but not elements. Muonic atoms are metastable bound states of a particle and its antiparticle; hadronic atoms are elemental ions which have been charge-balanced by accepting baryons or leptons other than electrons. They don't count as elements because they have completely different energy structures than the elements that make up the periodic table. 

In theory, you could argue that a muonic atom like protonium (the metastable bound state of a proton and an antiproton) is merely a hydrogen ion and an antihydrogen ion, but that's not quite right. Being in an energy-bound state means they have different mass than if they were apart. We don't say that Helium-4 is "merely two deuterium atoms".

11 hours ago, StrandedonEarth said:

"Neutronium" is generally used to describe the stuff that makes up a neutron star. Unimaginably dense stuff; simply pure neutrons, with none of the empty space you would 'see' between an atom's nucleus and its electron shell. It doesn't fit the definition of an element, but logically I would expect it should be considered an element in its own right. It would be just to the left of 'unobtainium'

Neutronium is a phase state of fermions, basically the same way that ice is a phase state of water or quark-gluon plasma is a phase state of quarks and gluons. It's not an element in any sense. 

[kerbiloid]

5 minutes ago, sevenperforce said:

hadronic atoms

And hypernuclei

[KAL 9000]

On March 16, 2016 at 1:19 AM, Darnok said:

Black hole is last "element".

But remember that elements are our creation only, they are like sections/paragraphs of matter, while matter itself is continuous.

This is from the guy who thinks the Aether is real and habitable solar systems must obey the Titus-Bode law .

But seriously, "matter is continuous"? Um... Atoms? Subatomic particles? And also, spacetime itself is "grainy". Ever heard of the Planck length and the Planck time?

Black holes are, to quote Doc from Back to the Future, "rip a hole in the space-time continuum". They're just holes in the space-time continuum caused by either a supernova (stellar-mass) or SUPER BIG gas cloud collapse (supermassive).

Edited March 17, 2016 by KAL 9000

[insert_name]

I heard that the last possible element was one that had its electrons so far out they were orbiting at relativistic speeds, not sure how big it would be, but the nuclear forces would be immense

[fredinno]

14 hours ago, kerbiloid said:

"Photonium" - a very common chemical element with 0 protons, 0 neutrons, 0 electrons.

That's not an element at all!

21 hours ago, StrandedonEarth said:

"Neutronium" is generally used to describe the stuff that makes up a neutron star. Unimaginably dense stuff; simply pure neutrons, with none of the empty space you would 'see' between an atom's nucleus and its electron shell. It doesn't fit the definition of an element, but logically I would expect it should be considered an element in its own right. It would be just to the left of 'unobtainium'

It should actually be left of Hydrogen, as it has an atomic number of 0. 

9 hours ago, sevenperforce said:

Those are (exotic) atoms, but not elements. Muonic atoms are metastable bound states of a particle and its antiparticle; hadronic atoms are elemental ions which have been charge-balanced by accepting baryons or leptons other than electrons. They don't count as elements because they have completely different energy structures than the elements that make up the periodic table. 

In theory, you could argue that a muonic atom like protonium (the metastable bound state of a proton and an antiproton) is merely a hydrogen ion and an antihydrogen ion, but that's not quite right. Being in an energy-bound state means they have different mass than if they were apart. We don't say that Helium-4 is "merely two deuterium atoms".

Neutronium is a phase state of fermions, basically the same way that ice is a phase state of water or quark-gluon plasma is a phase state of quarks and gluons. It's not an element in any sense. 

Well, you can have a Neutron with an electron orbiting it- it will decay in 15 minutes, but it seems to resemble an atom in every other way except by not having a proton https://en.m.wikipedia.org/wiki/Neutronium