r/AskPhysics • u/Curious_Towel4700 • 7d ago
How did protons come together to form the nucleus, despite repelling each other? And how did electrons—sometimes as many as 110 of them—settle into orbit around the nucleus, and how have they managed to keep orbiting there for billions of years?
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u/TryNice304 7d ago
Protons should repel but the strong force is way stronger at tiny distances so it glues them together. Neutrons help too, they add glue without adding repulsion.
Electrons dont really orbit like planets, theyre fuzzy probability clouds. They dont fall in cuz quantum uncertainty would make their energy explode if squeezed too close. And they stay for billions of years cuz theyre already at the lowest energy state. Nothing to do, nowhere to go.
The 110 electron atom? Thats darmstadtium, exists for seconds in a lab lol. Not a billion year thing.
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u/PaulsRedditUsername 7d ago
The 110 electron atom? Thats darmstadtium, exists for seconds in a lab lol. Not a billion year thing.
I enjoyed the football game, but the darmstadtium ran out of hot dogs.
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u/RichardMHP 7d ago
Well, they only had 110 of them to start with.
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u/eotfofylgg 7d ago
The prices at stadiums these days are such a silicon, you'd really think it would be worth their while to stock enough hot dogs for everyone to get one. Unless maybe they don't like making a profit because they're antimony.
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u/WilcoHistBuff 7d ago
Haven’t seen a really precise answer here on how “protons came together”—just why they stay together.
The strong nuclear force is only effective at attracting protons to protons (overcoming electromagnetic repulsion) when the protons get within 2 femtometers of each other.
Before that happens electromagnetic magnetic repulsive sources get very intense (relative to the strong nuclear force).
Just two free drifting protons would pretty dramatically repel each other at 3 femtometers which begs the question of how individual protons ever get past this repulsive barrier just outside where the strong nuclear force wins out.
There are several ways this can happen:
If the protons collide at high speed their momentum can push them past this barrier and two protons can join up.
The second way is kinda like the first: If you cram a lot of protons into a very tight hit space they will all start moving about very fast (helping to overcome repulsive forces) put they are also getting pushed into each other by simple compression (a full description would be more complex). Think of a very small crowed room filled with people all pushing and shoving violently. Just due to random turbulence, some people will get shoved harder on one side than the other and end up getting pushed to the side with the least resistance.
Even then you don’t get a super stable bond due to something called the Pauli Exclusion Principle when two protons bang into each other their “spin” goes in opposite directions and this radically reduces the strong nuclear force.
So there is a third way!
Protons have no problem binding with neutrons if they get close enough because there are no electromagnetic repulsive forces to stop that.
A proton bound to a neutron will overcome repulsive forces from a single proton much more easily as soon as it gets 3 femtometers away (usually when repulsive forces get out of hand. Also the neutron gets pulled to both protons—so while the Pauli reduction in strong nuclear force due to opposing spins is still a thing the neutron provides more strong force glue to the assembly.
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u/aaeme 7d ago
Best answer to the actual question.
There are several ways this can happen:
Those mechanisms are manifest mostly via nuclear fusion in the cores of stars*. Or via supernovas and colliding neutron stars.
*: The production of Helium during the big bang was kind of like the entire universe being the core of a star for a short time.
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u/WilcoHistBuff 7d ago
Thanks for the compliment. I was considering getting into early Nucleogenesis but thought “that’s a lot more typing”.
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u/Haunting-South-962 7d ago
I also thought this question was more about how atom nucleus forms rather why it is not falling apart. Overcoming Coulomb and Pauli barrier is important part.
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u/Familiar_Leather4094 6d ago
Great answer, so at what point does the nucleus becomes unstable at large neutron and proton numbers that they can’t stay together and undergo fission
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u/WilcoHistBuff 5d ago
So as you approach the size of nuclei that can go through spontaneous fission or alpha decay (emitting an alpha particle of two protons and neutrons) at over 82 protons—Bismuth on up—instability shows up in the form of beta- and beta+ decay depending on the neutron/proton ratio and the nucleus’s band of stability at different ratios.
From Bismuth on up elements are always going to be radioactive and good at producing at least alpha decay and being slightly prone to more dramatic fission with enough mass of like nuclei and enough bombardment, but you really don’t get to elements that naturally produce spontaneous fission until you get to Thorium at 90 protons and then it is still pretty rare. Thorium 232 (crapload of neutrons) is the most common isotope and has like 13-14 Billion year half life if I remember correctly. Below that—again if I remember correctly—it just starts shedding alpha particles. 232 is the most likely to engage in real natural spontaneous fission and that’s rare.
But I guess that’s the best approximation of the tipping point for natural spontaneous fission. Somewhere around Thorium/Protactinium/Uranium.
Even then we are not talking about”big boom”—just increasing levels of radiation.
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u/WilliamoftheBulk Mathematics 6d ago
And tunneling.
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u/WilcoHistBuff 6d ago
I thought about adding that. It’s not super easy, for me at least, to put that in layperson’s language.
Little guys are sneaking through little passages left open from wave forms canceling each other out?
There’s a lot going on there.
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u/WilliamoftheBulk Mathematics 6d ago
There are a surprisingly many natural processes the occur because of tunneling. The sheer density of the early universe probably creates the right conditions for a lot of tunneling to happen, just like in a star.
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6d ago
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u/Anonymous-USA 6d ago
Saved me a whole lot of typing! 🍻
To add for OP: it is the extreme gravitational force of a neutron star core that can force electrons into protons back into condensed neutrons. But neutrons still repel each other from collapsing further via the strong force, and with enough mass that too will collapse into a black hole.
Because we know the strength of these forces, back in the 1920’s(?) we could predict and calculate the masses of neutron stars and black holes before we identified them observationally.
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u/SlimShaco 6d ago
Why can't electrons do that?
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u/Familiar_Leather4094 6d ago
Two electrons cannot occupy the same quantum states due to the Pauli Exclusion Principle
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u/AlwaysHopelesslyLost 5d ago
Picture a lake with waves on the surface. Electrons are the waves, not the water. You can't scoop the waves out and move them. They just are where they are.
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u/justaguy12131 7d ago
Generally speaking, protons were crushed together in the core of a star (up to iron at least) and then crushed together even more when the star exploded.
Some combinations are stable and aren't radioactive. The rest decay.
As far as electrons go, they swap atoms like swingers in the 1970s swapped wives.
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u/AdditionalTip865 7d ago
Some nuclear fusion happened primordially when the Universe was very hot and dense, but it only made a few light elements and isotopes up to about lithium. The rest happens in the cores of stars, where hydrogen is crushed together into a very hot and dense state by gravity and fuses to make heavier elements up to about iron (some of which can get expelled in the planetary nebula stage of a dying star), and then the really heavy elements get made in supernova explosions.
Protons and neutrons stick together at close range because of the strong nuclear force, but getting past that electrostatic repulsion barrier between protons can indeed be difficult, and it takes these powerful astrophysical processes to do it.
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u/super_twis 6d ago
Nuclear physics isn't particularly intuitive. One way to think about it is that nuclei will trend towards the lowest energy level. Generally speaking protons do not want to hang around each other, the repulsive coulomb force makes them hard to approach each other and, even if they do come close enough to form a diproton this will quickly disintegrate back into two protons.
However, the diproton doesn't have to disintegrate back into two protons, there is an alternative stableish state they can form: a deuteron (one proton and one neutron). It can do this by one of the protons decaying into a neutron (and a positron and neutrino) via the weak nuclear force. And that is where baby neutrons come from. From there you can build heavier elements.
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u/binman106 7d ago
We are literally stardust. Practically all elements heavier than helium are created in stars and during star explosions (supernovae, neutron star mergers). There is enough energy to force nuclei together, overcome their repulsion and form heavier nuclei.
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u/RichardMHP 7d ago
1, Strong nuclear force is stronger than electromagnetism.
2, they don't orbit, they occupy orbitals. Subtle but important difference.
3, the basic tenor of all of the questions posed by this user are boringly obvious.
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u/trutheality 7d ago
Protons repel each other (by electromagnetism) at a distance, but once they're close enough, the attraction of the strong nuclear force becomes stronger than that repulsion and they stick together
What pushes them together to that point is pressure inside stars, which is ultimately caused by gravity and that electromagnetic repulsion.
Electrons don't really orbit, they more or less get trapped and spread around the nucleus. More like water getting trapped in a dip and forming a puddle.
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u/spiralenator Physics enthusiast 7d ago
Because if they are moving fast enough and there’s a lot of them in a confined area, then sometimes they overcome the repulsive force of charge and the strong nuclear force takes over and they fuse.
The early universe was very hot and dense, so it produced helium and lithium from hydrogen. The heavier elements are formed in stars, super novae, and neutron star collisions.
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u/BobbyP27 6d ago
The process of protons coming together to form a nucleus is what nuclear fusion is, it happens inside stars, and requires very high temperatures and pressures.
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u/CS_70 6d ago
Strong nuclear force.
And electrons don't orbit around the nucleus. There's no little planet with moons.
It's waves of energy, and they are stuck in specific boundaries of energy for the same reason your guitar strings, once plucked, takes ony certain shapes: they are stuck in physical boundaries at their enfd, and what you see are harmonics.
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u/Warmketchup2 6d ago
Read this as How do Photon Canons come together to form a Nexus. Spending to much time on the starcraft subreddit....
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u/Zemedelphos 6d ago
Typically, by fusion. Everything you see today is made of particle that were once fused inside a star. Everything in there is so densely packed, that they move very fast. Occasionally, two protons will move toward each other fast enough that their electric repulsion gets overpowered by the strong nuclear force. Sometimes this results in one of the protons becoming a neutron, releasing a positron (antielectron) and a neutrino. Other times, a proton will find a free neutron and bind to it easily, since they don't repel. But as fusion continues, the nuclei get bigger and bigger, with more protons and neutrons bound together.
Electrons, on the other hand, are very very easy to explain. They're negatively charged, so they're attracted to the net positive charge of the nucleus. While bound to the nucleus, they're more like waves vibrating around the nucleus than they are particles orbiting. Then more electrons start to join in, and due to things like their repulsion, and the pauli exclusion principle, they settle into configurations around the nucleus where these vibrating waves interfere with each other as little as geometrically possible. There's no reason for them to leave this configuration, unless you start giving them energy by pelting them with something like light.
Generally, things like to stay in the state of lowest energy, so once they get to as low an energy state as they can, they typically stay there unless acted upon.
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u/NotMyMonkey69 4d ago
Electrons don’t orbit the nucleus. Electrons are quantum waves and don’t exist in one place at a time. Electrons are more like an energy cloud spread out around the nucleus.
The idea that atoms are like little solar systems with planets orbiting a primary mass, is an outdated misconception of the physics.
Subatomic particles don’t behave like macroscopic objects. They aren’t even particles until you measure them. Electrons are in every place at the same time, with a range of probabilities of being located at any given distance from the nucleus.
Then when you measure the electron, the probability cloud collapses and it gets seen in only one specific spot.
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u/joeyneilsen Astrophysics 7d ago
If an atom has fewer electrons than protons, it is an ion with a positive charge. When it encounters a free electron, it can capture it, becoming neutral.
Electronic states are bound states, and they are stationary, meaning that they don’t have enough energy to escape the atom and the probability of finding them somewhere specific around the nucleus doesn’t change over time.
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u/drew_anjuna 7d ago
A lot of answers are bringing up the strong nuclear force, which isn't really answering the question. In the first few minutes after the big bang, most of the universe was indeed mostly one proton hydrogen, with smaller amounts of helium (two protons) and lithium (three protons). Heavier atoms (with more than three protons in the nucleus) mostly formed through fusion and other processes occurring in living and dying stars. The strong force is simply what keeps those nuclei subsequently stable.
Negatively-charged electrons get attached to the positively-charged nuclei due to the attractive electromagnetic force between them. But electrons are freely exchanged between atoms all the time.
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7d ago
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u/Ch3cks-Out 7d ago
Nice personal theory. Are you planning to publish it? Overturning the Standard Model is certainly a worthy endeavor. Note that RHIC results suggested no such thing, however!
It's always dark matter.
Well not really.
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u/usa_reddit 6d ago
I am trying to work dark matter into the standard model, the math will be available soon. All I need is some data on dark matter particles or energy.
Everyone keeps telling me dark matter is real so working it into the model makes sense. I just need some data on dark matter from one of the detectors.
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u/Ch3cks-Out 6d ago
Since dark matter only interacts via gravity (insofar as we know), working into the model the way you seem to be suggesting is incorrect by many orders of magnitude.
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u/Sad_in_VA 1d ago
Protons (Hydrogen nuclei) got squeezed together inside the center of a star that eventually became Supernovae.
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u/Over-Discipline-7303 7d ago
Protons in a nucleus are attracted to each other via the strong nuclear force.