Are There An Infinite Number Of Elements?

There are currently 118 elements in the periodic table, but could there be more? In the first Polyhedral video, we discuss the physics and chemistry behind the question "Could there be an infinite number of elements?". We'll chat a bit about the history of the science, including what Richard Feynmann predicted the limit might be. Beyond that, we'll explore the periodic table of elements and chat about up-down quark matter, a potential theoretical concept for heavy matter.

References:

[1] “The Technical Details: Radioactive Decay.” 2002. Global Monitoring Laboratory.

[2] Napy1kenobi. “Chart of the nuclides showing the ratio of protons to neutrons, with a black 'Island of Stability' in a 'Sea of Instability.”.

[3] Zagrebaev, V. 2016. “Opportunities for synthesis of new superheavy nuclei (What really can be done within the next few years).” 11th International Conference on Nucleus-Nucleus Collisions.

[4] Ball, Philip. 2010. “Column: The crucible | Opinion.” Column: The crucible | Opinion | Chemistry World.

[5] Scientific Opportunities with a Rare-Isotope Facility in the United States. j7st 2006. N.p.: National Research Council.

[6] “Unseptbium.” The Elements Wiki.

[7] Holdom, Bob. 2018. “Quark Matter May Not Be Strange.” Physical Review Letters.

[8] Holdom, Bob; Ren, Jing; Zhang, Chen. 2018. “.Quark Matter May Not Be Strange.” Physical Review Letters.

Chapters:

00:00 - The Foundation & Nuclear Physics
02:22 - What Did Feynman Think?
03:12 - What Do We Know Today?
04:28 - The Next Video

Music:

Steve O'Brien - Popcorn
Howard Harper-Barnes - At Evenfall
Lama House - The Road to Odessa

#Physics #Chemistry #Science

[PolyhedralMedia]

If you enjoyed this work, you can support it here on Patreon: patreon.com/Polyhedral

Video Transcript:

There are currently 118 elements in the periodic table, but could there be more? Maybe there’s an infinite number and we could eventually discover unobtanium…

But, let’s forget about unobtainium for a minute and take a look at good old, ubiquitous carbon.

Elements are defined by the number of protons they have, so carbon is carbon because it has six protons. It also has six and a bit neutrons… A bit, because it has three naturally occurring isotopes. An isotope is how we distinguish elements that have the same number of protons, but different numbers of neutrons. Carbon-12 and -13 are stable, but their heavier cousin -14 is radioactive [1], and has a half life of around five and a half thousand years.

The half life is a measure of the time it will take for half of the atoms in a material to radioactively decay. That’s how we do carbon dating, we just check how much carbon-14 is left in something, compared to if it was new.

Fortunately for us, most carbon isn’t radioactive, and five and half thousand years is pretty damn long, so we don’t exactly consider carbon to be a radioactive element. As elements get heavier, they tend to become less and less stable. In fact, these elements don’t have any stable isotopes.

Each square in this graph is a different isotope of every element we’ve ever discovered [2]. This black line shows all of the isotopes that are stable, this is called the valley of stability, and every other isotope is radioactive in one way or another. But why does the valley end after the elements have more than 82 protons?

To explain this, let’s take a look at a stable nucleus and how it’s neutrons and protons interact with each other. There are two fundamental forces at play here: the ‘strong nuclear force’ and ‘electrostatic repulsion’. The strong nuclear force is a force that holds neutrons and protons together, much like how gravity pulls us towards the Earth. Conversely, electrostatic repulsion causes protons to repel one another. So as elements get heavier and heavier, the number of protons will increase and this repulsion becomes larger and larger, eventually out-strengthening the formerly strong, strong nuclear force and all heavy elements eventually become unstable.

At a certain point, this repulsion will be so large that elements won’t be able to form in the first place. This isn’t good for a hope for an infinite number of elements.

To understand why, let's look at the predicted half lives of isotopes with more than 82 protons. If we quickly draw an extension of the valley of stability we see that these elements are radioactive, but have quite long half lives, but the further we move from this line, the less and less stable these isotopes become, with shorter and shorter half lives [3].

But, if we zoom out a little bit further, we find this… the Island Of Stability, where a cluster of isotopes have uncharacteristically long half lives. But this doesn’t quite answer the big question, how large can an element get?

There’s a bit of a “folk legend” amongst physicists that Richard Feynmann once did a back of the envelope calculation to show that any element with an atomic number of 137 or greater would have it’s lowest energy electron travelling faster than the speed of light [4], which is impossible! In reality, if this folk legend is true at all, this was likely just a playful exercise, rather than any proper science.

In a more serious bit of science, Feynmann did confirm that elements above an atomic number of 137 might cause some issues. This, slightly scary looking equation tells us the energy of an electron. If we look at elements with more than 137 protons, it turns out their energy would have a square root of a negative number in it. This is definitely breaking the rules a bit and is often a handy tool physicists use to prove the non-existence of something.

But, this also turned out to be a little bit of an oversimplification. Feynmann assumed that the nucleus would be nice and spherical, but in current scientific understanding, it would look more like this [5], with modern calculations presenting the possibility of elements all the way up to an atomic number of 172 [6].

Since then, a range of potential extensions to the periodic table have been presented, each of which ending somewhere around 172 elements.

However, some theoretical physicists have gone a bit further than that and come up with a hypothesis called the Continent of Stability [7]. The idea is that if nuclides get heavy enough, then they would no longer simply be atoms with neutrons, protons and electrons, but rather, the neutrons and protons are broken apart into up and down quarks. This would result in a kind of free flowing soup known as up-down quark matter [8], and could probably only exist under the collosal pressure of a supernova or the famously dense neutron star.

Whilst these aren’t really elements any more, because they don’t have neutrons, protons and electrons, they can keep increasing in mass somewhat indefinitely and are even stable to certain types of radioactive decay, so maybe they’ll be the key to finding heavier and heavier particles.

So, we don’t know exactly, but based on our current understanding of physics, we know that the periodic table may end somewhere around atomic number 172 and that unobtanium probably is unobtainable, but the continent of stability may be our route into understanding heavier and heavier matter.

I hope you enjoyed watching. In the next video, we’ll discuss how this ambitious looking doughnut could be the solution to both the climate crisis and global inequality. So If you enjoyed this be sure to subscribe and click the little bell icon, and if you really enjoyed it, I’ve just launched a Patreon page where you can support this work. Thanks!



References


[3] Zagrebaev, V. 2016. “Opportunities for synthesis of new superheavy nuclei (What really can be done within the next few years).” 11th International Conference on Nucleus-Nucleus Collisions.


[5] Scientific Opportunities with a Rare-Isotope Facility in the United States. 2006. N.p.: National Research Council.



[8] Holdom, Bob; Ren, Jing; Zhang, Chen. 2018. “.Quark Matter May Not Be Strange.” Physical Review Letters.

[natekloepfer]

Another reason why lead/bismuth are the last elements with stable or near-stable isotopes is that the 82-proton and 126-neutron combination creates a "doubly-magic" nucleus. This is also why elements like polonium and radon (immediately after lead and bismuth) have very short half-lives.

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[ShubhamGahtori]

Really great explanation sir!
I hope you keep progressing.
Recently I read about the Island of Stability and now I understand it better.
Chemistry is certainly full of surprises!
New trends appear all of a sudden and change the whole scene.
I love how this subject embodies 'order in chaos' so perfectly!