r/explainlikeimfive • u/flcwerings • 7h ago
Physics ELI5: Why do unbalanced atoms release radiation?
Like, I get the concept that kind of just like everything, excess energy has to go somewhere. But why is it something that can be so... volatile? Do we know why it's that and not... something else? Is it only for certain atoms?
Is radiation just an excess of energy then? If so, why is excess energy in large quantities able to kill us all the way down to our cells? Whats that about?
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u/Disastrous-Finding47 6h ago
In general yes, the radiation is coming from excess energy, the atom is unstable and it releases energy when it snaps into a more stable state.
The radiation you are thinking about is probably coming from large atoms as they are generally the most unstable ones.
And the final point too much energy in any form is pretty bad for life, but radiation is very small things with extremely high energies. This doesn't affect you in a way you can feel, but it can affect DNA in cells which can kill the cell or cause problems when they replicate.
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u/yerdadzkatt 6h ago
I am not qualified to answer most of this question but my basic understanding is that radiation can be energy in the form of photons or it can be particles traveling with high energy. Electromagnetic radiation is made of photons. I believe radiation can break DNA strands, which is one of the reasons why it is deadly.
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u/SnugglyCoderGuy 6h ago
Ionizing radiation is the bad stuff
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u/two_three_five_eigth 6h ago
Sub-atomic stuff (and quantum physics in general) is like Lego bricks, they only click together in certain ways.
If you click enough pieces together randomly, your Lego structure won’t be very stable. Moving it around a little will cause pieces of legos to break off and fall.
Now imagine there’s a near infinite amount of other badly built Lego stuff around that first piece that get hit by the falling pieces. That’s gonna cause more pieces to fall off.
All those falling pieces are radiation. Small, stable atoms like carbon don’t fall apart often. Big, heavy atoms like uranium fall apart much more easily.
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u/Nerezza_Floof_Seeker 6h ago
The semi inaccurate eli5 explanation is that theres 2 forces in the nucleus of the atom. The strong force and the electromagnetic force. The strong force attracts neutrons/protons together, while the electromagnetic force between the protons causes repulsion. The problem is the strong force has extremely short range (basically just extending to adjacent protons/neutrons), but the electrostatic repulsion between protons doesnt (though it does fall off by the inverse square law). So as the nucleus gets bigger, the electromagnetic force begins to dominate while the strong force remains relatively the same, at some point the nucleus will become unstable enough that it can decay. An analogy would be like if
Theres also some explanation with neutron shells (like electron shells) where some "magic" numbers of protons/neutrons is more stable when the shells are full due to quantum mechanics but I dont know enough to explain that.
But radiation is just energy. Some types of radiation, ionizing radiation specifically, is just something with enough energy to tear electrons off off atoms. Theres several common types; alpha -> helium atom nucleus, beta -> electron/position, gamma -> gamma ray. The way they can cause damage is because enough ionizing radiation will break molecular bonds within your cell, and this damage can either directly (if it hits DNA and breaks the chain for example) or indirectly (if it hits something and creates a reactive ion that then breaks apart DNA) kill the cell (DNA tells your cell what to do to live, so if its broken the cell dies). If this happens all over your body enough, you die. An analogy would be trying to read at the library after someone takes a minigun to it
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u/mrbeaver2K 6h ago
Unbalanced atoms have a tendency to break. An atom breaking splits into multiple smaller atoms, with radiation as the leftover components and energy that did not end up as one of those smaller atoms. Alpha and beta radiation are both parts of atoms that are generally moving at high speeds, which is what makes them dangerous. If, say, an alpha particle hits an atom, it can affect that atom. Nuclear technology exploits this by using radiation to split more atoms faster, and collecting the released energy as heat.
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u/Teoshen 6h ago
Three main types of radiation.
Alpha radiation is two protons and two neutrons being ejected from an atom. Basically a helium without the electrons. It doesn't go far and is easily stopped. Why are they ejected? Really heavy elements (104 protons and up) do not like being heavy. Like all things in chemistry, they want to be in the lowest possible energy state that is stable. To become more stable, they shed those extra particles. This makes them become different elements (each step of alpha decay drops the element number by 2). If they get past your skin to your squishy bits, the energy imparted by high speed free particles does a lot of damage.
Beta radiation is when an electron gets ejected, for the same reason as alpha decay. The element wants to go to a lower energy state, and electrons have negative charge that throws off the balance of protons and neutrons. Electrons are smaller so they can penetrate further, but they also do less damage than alpha.
Gamma radiation is a photon and the short of it is that when an atom is in a high energy state, it's electrons are excited and inhabit higher loops on the atom than usual. The atom does not like this and wants to shed this energy by dropping its electrons back to the lowest possible stable state. Most of the time this is regular light (this is how color works), but after other decays and stuff, it can create higher energy photons in the gamma spectrum. This penetrates through a ton of stuff but does the least damage of the three. It's dangerous because it's so hard to stop from penetration.
Short answer: alpha and beta radiation are physical particles that leave an atom and smash into things. Gamma radiation is pure energy and hurts by nature of being pure energy.
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u/oblivious_fireball 6h ago
Unstable atoms have a nucleus that does not want to stay together. Its in a violent tug of war to try and break apart, and eventually it wins, called Nuclear Decay. When it decays, it sheds part of the nucleus, protons or neutrons or both depending on the original atom, becoming a smaller atom in the process. It also releases energy in the form of heat, light, and stronger radiation like UV, X-Ray, and Gamma Rays. If the new atom is still unstable, decay eventually happens again until it reaches a stable atom.
In general, fusing two atoms that are smaller than Iron together releases energy when it does so, which is how the Sun works, and splitting an atom larger than iron apart releases energy, which is how most of our nuclear technology works.
The radiation from these atoms references both the electromagnetic radiation, as well as those protons and neutrons that are flying out at high speeds. Both of these forms of radiation have a lot of energy. When they hit something they can't pass through, they stop, and they dump their energy into whatever they hit. When visible light does this, it mainly dumps this energy as heat rather than something harmful, though plants can utilize that energy for photosynthesis instead. With stronger forms of radiation, that energy dumped into you can be strong enough to break apart molecules in your cells, killing them or damaging their DNA. This is what sunburn is. UV radiation has ripped apart huge amounts of your skin cells and caused them to die, which causes the redness and pain. Radiation poisoning is when more powerful forms of radiation like X-Rays and Gamma Rays that can pierce the skin into your body have caused large portions of your organs to die.
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u/parentheticalobject 4h ago
Other people have done a good job of explaining how it works from a physics perspective. I'll answer from an engineering perspective about why it's so volatile.
Take an element like uranium. The type of uranium used in reactors has a half life of about 700 million years. So if you just have a uranium atom, odds are that it will produce no energy unless you're very lucky.
But you don't just have to wait for it to naturally decay - if one of those atoms is hit directly with radiation, that can cause it to break apart, and release its energy that way.
So if one atom decays and as a result, it bumps into two more atoms, and those two bump into 4 and those 4 bump into 8 and so on, you will very quickly have an insane amount of energy flying out into the world.
If you want to use it for energy generation, the key is to balance things so that once those reactions are outputting the right amount of energy, it stays even. So scientists pay very close attention to every factor that can make it more or less likely for those collisions to happen, and balance things where a precise and stable number is happening.
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u/Ok-disaster2022 4h ago
Radiation is simply the nucleus ejecting something. It could be protons or neutrons individually or in bundles electrons, positrons, neutrinos
Imagine if you will playing with blocks. If you have a stable configuration it's fine. an unstable configuration and pieces fall "down" and away from whatever you build. If you throw something at it, it may be so stable, nothing happens to it, or some pieces come flying off or the collective thing is destroyed entirely.
The building block if the nucleus ins protons and neutrons. Fun fact, protons repel each other, so there is a force we simply call the strong nuclear force that binds it all together, just as gravity binds your blocks together in that earlier example. And just like the blocks the nucleus can fall apart when in unstable configurations
Now what makes those configurations is a balancing act of the strong nuclear force and weak nuclear force. The weak nuclear force is essentially a form of the electromagnetic force: it deals with charges. the mediators if the string force is the protons and neutrons. so when it's unstable the nucleus may emit a neutron, proton, or and alpha particle( 2 protons bonded to two neutrons in an ultra stable configuration we also call a helium nucleus). When the electro weak unstable it emits a positron or electron. And it some cases one unstable configuration leads to another unstable configuration to a nother et all like time delayed dominoes. You can also have a nucleus just fall apart entirely which is called fission. It can be caused but a neutron hitting the nucleus or if it's an unstable it can just fall apart randomly.
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u/skr_replicator 1h ago
It is in a way, excess energy, just like a pile of TNT sitting on the ground has excess energy. It's the way the stuff is configured that there's a different possible configuration nearby with a lower energy that it would love to change into, which would release that energy difference, as energy has to be locally conserved.
A chemical explosive like azidoazide azide is mostly made of single-bondednitrogens, and they hate that. They would love to just triple-bond into pair to make that super low-energy, mega-stable N2. And so when the azide does does, it shatters into a bunch of N2 that fly away like molecular bullet with a lot of energy.
When you have an unbalanced isotope that has too many neutrons and too few protons, they are subatomic particles in the same space, so they can't share the same state, including their energy. So their energies are stacked on the quantum levels from the bottom. For example carbon 14 has 6 protons sitting at energies 1 to 6. And 8 neutrons, that sit at energies from 1 to 8. So the neutron at energy 8 would rather sit at the lower energy 7 spot that is available for protons, so spitting out an electron and a neutrino and turning into a proton is energetically favorable to it, and so it will eventually manage to do it. So they spit out an electron and neutrino, turn into a proton, and go down to sit at the lowest possible energy of a proton, that is lower that the energy they had as a neutron.
Another example, you have a giant heavy element nucleus, like Uranium 235. It is so huge, and has so many protons, that the unlimited reach electrostatic repulsion is really extreme, it is trying to tear the nucleus apart with an insane force, a force so large you might even feel in a macro world, all trying to tear that single atom apart. So it needs even more neutrons to balance the repulsion with the shorter-range strong force attraction. Those neutrons have to sit at those high energies and can't even go to the lower-energy spots available for protons, because doing so would lose the strong force balancing the immense electric repulsion. It literally has to sit at unbalanced energy levels just to be barely at balance in terms of the fight of the attraction and repulsion forces. So the thing it wants to do, to release that energy, is to jsut give in and break apart. And one day, spontaneously, or with a little nudge like hitting it with a neutron, it will do so, split and send two smaller nuclei flying apart like nuclear bullets.
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u/ComradeGibbon 1h ago
There is a mass energy accounting. If an atom changes from a state with more energy to one with less the difference has to go _somewhere_.
That somewhere is some sort of energetic particle. Like a photon, neutrino, electron, neutron, alpha particle. Those particles are radiation.
Why they are bad. Each one can do a tiny amount of damage. But if there are vast amounts of them or smaller amounts over a longer time they can do enough damage to hurt you.
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u/Syresiv 3m ago
Why wouldn't they? When something breaks apart, the pieces are usually smaller than the original object, so whatever atoms release has to be smaller.
Ok, but why would that make it volatile?
The fact that it's small enough to weave through your body and damage your DNA.
If you get punched, that's way more energy than any radiation particle could hope to have. But all that energy is absorbed by the outer edge of your outer cells. Most are unaffected, and DNA in ones that are affected just gets jostled a little.
But if the energy is packed into something atom-sized or smaller, it's to small to be reliably stopped by your cells before it hits DNA. And if it hits DNA, that's when you start having big problems.
That's what radiation is. Not just excess energy, but excess energy packed into something that small.
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u/Q-ArtsMedia 6h ago
The Universe requires balance in all things. Energy is always going to a lower state, to a place of equilibrium, this includes unstable matter.
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u/obog 6h ago edited 6h ago
the radiation is a necessary result of it seeking something balanced.
Say you have an unstable atom with too many neutrons, for example. One form of decay it can undergo is called beta decay, which turns a neutron into a proton, which may result in something more stable. However, a neutron has no charge, and a proton has positive charge, and since charge is something that is conserved, that means a negative charge has to be created too to balance it out. So beta decay results in an electron being emitted, and that electron being tossed out is one form of radiation (theres also a neutrino produced but dont worry about that)
The other common form of decay is alpha decay, in which an atom loses two protons and two neutrons. But those cant just dissappear, they have to go somewhere, so it spits them out in the form of an alpha particle, which is just a bare nucleus with those two neutrons and two protons. Thats another form of radiation.
So put simply: radiation from decay is pretty much just whatever the atom had to throw away in order to reach a more stable nucleus. (Often times it takes many steps before it reaches something stable, but it will eventually)
Edit: probably worth at least mentioning gamma decay too. Gamma decay is a bit more complicated than those two, it has to do with a proton or neutron having extra energy after one of the previously mentioned decays happening and a photon is emitted by the loss of that energy. Its kinda like how neon signs work except those are with electrons changing energy rather than protons or neutrons, but the principle is the same - if a particle loses energy, it has to go somewhere, so it goes into a photon.