EDIT: Thanks for all the responses!
In: 3337
Protons are all positively charged, so they repel each other. In atomic nuclei, there’s a force called “strong force” which holds them together, and for most atoms that force is altogether strong enough that they’re stable that way. The strong force has a very short range, while the electromagnetic repulsion doesn’t. So when a nucleus is sufficiently big, the nucleons on one side of it don’t even contribute to holding the nucleons on the other side of it together, but protons on opposite sides still repel each other.
It’d also maybe help with adding more protons to a nucleus if there was a way of doing it gently. But the only way humans have for now of putting nuclei together is essentially bombarding one kind of nuclei with another and having some not miss by sheer number, resulting in fusion (a nucleus is very small even compared to the full size of the atom with its electrons.) Fast bombardment is necessary because the repulsion would probably deflect slower nuclei. It’s not like we have a femtoscopic vise and tweezers to keep sticking more nucleons onto an immobilized nucleus.
Protons are all positively charged, so they repel each other. In atomic nuclei, there’s a force called “strong force” which holds them together, and for most atoms that force is altogether strong enough that they’re stable that way. The strong force has a very short range, while the electromagnetic repulsion doesn’t. So when a nucleus is sufficiently big, the nucleons on one side of it don’t even contribute to holding the nucleons on the other side of it together, but protons on opposite sides still repel each other.
It’d also maybe help with adding more protons to a nucleus if there was a way of doing it gently. But the only way humans have for now of putting nuclei together is essentially bombarding one kind of nuclei with another and having some not miss by sheer number, resulting in fusion (a nucleus is very small even compared to the full size of the atom with its electrons.) Fast bombardment is necessary because the repulsion would probably deflect slower nuclei. It’s not like we have a femtoscopic vise and tweezers to keep sticking more nucleons onto an immobilized nucleus.
Oganesson, element 118, is just where we’ve got up to *so far*. It makes the periodic table “look finished” but that’s just coincidence right now and we are trying to make element 119 and beyond.
Part of the problem is that the more protons a nucleus has, the more neutrons per proton it needs for maximum stability. So when we fuse two smaller nuclei to get one with lots of protons, there’s not really enough neutrons in the product. For everything from Bohrium (element 107) onwards, the most stable isotope we know is the one with the most neutrons. They might have more stable isotopes we haven’t discovered yet – although “more stable” for the superheavy elements is likely to mean half lives of a few hours at most.
Making it even harder is to get up to Oganesson we bombarded target isotopes with Calcium-48 – 20 protons, 28 neutrons. That helped with the neutrons per proton issue. Even then, it’s rare that the fusion we want actually happens. But to make element 119 that way we’d need a target of element 99, Einsteinium, and we haven’t made enough of *that*. So we either need to make a lot more Einsteinium or use a different isotope for the “projectile”, and the second choice is what researchers are trying, but projectiles with more protons aren’t as good on the neutron:proton ratio.
It is reckoned that at some number of protons, no isotopes will be stable enough to form atoms, but theories don’t agree on what that number is. It takes a few femtoseconds for the electrons to gather around the nucleus so that’s what imposes the minimum half life to call something an “element”. Some theories also find that at some number of protons the atom can’t hold onto all its electrons because the outer ones would need to travel faster than light, but again, theories don’t agree on the details.
Haven’t seen this answer yet, so I’ll add it here. There comes a point in adding electrons where they’ll have to move faster than the speed of light for everything to work, and according to our current understanding of physics, that is impossible. So while it may be possible to find an island of stability we can create past the current limits of the periodic table, we more than likely wouldn’t be able to go past the point where the electrons would break laws of physics.
I wish I remembered the atomic number that phenomenon occurs at. I read it in a book called The Disappearing Spoon by Sam Kean and it was in the section about creating new elements and islands of stability past the current limits of the periodic table.
Oganesson, element 118, is just where we’ve got up to *so far*. It makes the periodic table “look finished” but that’s just coincidence right now and we are trying to make element 119 and beyond.
Part of the problem is that the more protons a nucleus has, the more neutrons per proton it needs for maximum stability. So when we fuse two smaller nuclei to get one with lots of protons, there’s not really enough neutrons in the product. For everything from Bohrium (element 107) onwards, the most stable isotope we know is the one with the most neutrons. They might have more stable isotopes we haven’t discovered yet – although “more stable” for the superheavy elements is likely to mean half lives of a few hours at most.
Making it even harder is to get up to Oganesson we bombarded target isotopes with Calcium-48 – 20 protons, 28 neutrons. That helped with the neutrons per proton issue. Even then, it’s rare that the fusion we want actually happens. But to make element 119 that way we’d need a target of element 99, Einsteinium, and we haven’t made enough of *that*. So we either need to make a lot more Einsteinium or use a different isotope for the “projectile”, and the second choice is what researchers are trying, but projectiles with more protons aren’t as good on the neutron:proton ratio.
It is reckoned that at some number of protons, no isotopes will be stable enough to form atoms, but theories don’t agree on what that number is. It takes a few femtoseconds for the electrons to gather around the nucleus so that’s what imposes the minimum half life to call something an “element”. Some theories also find that at some number of protons the atom can’t hold onto all its electrons because the outer ones would need to travel faster than light, but again, theories don’t agree on the details.
To add onto why it’s so hard…
Only one isotope of element 118 has been experimentally observed – Oganesson 294. It has a (predicted) half-life under 1 millisecond. So, after a tenth of a second, that’s over a hundred half-lives. If we start out with 8×10^31 atoms, we will have just one (on average) after just a tenth of a second – assuming there’s no chain reactions. For reference, Avogadro’s constant (the number of atoms in a mole) is about 6×10^23, and a kilogram of Oganesson has around 3.3-3.4 mol in every kilogram. We don’t really have a solid value because we have only detected five or six atoms of the stuff.
It may be the case that later elements on row eight are more stable. It’s even theorised that more stable forms of Oganesson exist… But that’s what we are dealing with here. Elements so unstable that even the stable ones evaporate into nothing in a matter of mere seconds.
Haven’t seen this answer yet, so I’ll add it here. There comes a point in adding electrons where they’ll have to move faster than the speed of light for everything to work, and according to our current understanding of physics, that is impossible. So while it may be possible to find an island of stability we can create past the current limits of the periodic table, we more than likely wouldn’t be able to go past the point where the electrons would break laws of physics.
I wish I remembered the atomic number that phenomenon occurs at. I read it in a book called The Disappearing Spoon by Sam Kean and it was in the section about creating new elements and islands of stability past the current limits of the periodic table.
To add onto why it’s so hard…
Only one isotope of element 118 has been experimentally observed – Oganesson 294. It has a (predicted) half-life under 1 millisecond. So, after a tenth of a second, that’s over a hundred half-lives. If we start out with 8×10^31 atoms, we will have just one (on average) after just a tenth of a second – assuming there’s no chain reactions. For reference, Avogadro’s constant (the number of atoms in a mole) is about 6×10^23, and a kilogram of Oganesson has around 3.3-3.4 mol in every kilogram. We don’t really have a solid value because we have only detected five or six atoms of the stuff.
It may be the case that later elements on row eight are more stable. It’s even theorised that more stable forms of Oganesson exist… But that’s what we are dealing with here. Elements so unstable that even the stable ones evaporate into nothing in a matter of mere seconds.
Think of stacking pizza boxes on top of each other. Sure, you can stack 100 of them, but the stack will be unstable and it’s difficult to achieve.
Similar thing here.
Absolutely. But most of those are going to be radioactive with very short half-lives such that they fall apart almost immediately. I remember when I was in highschool that it was theoretically predicted that there might be a stable element at 126 protons, but I don’t know if that’s still considered a thing.
Latest Answers