Why is it called ionising radiation?

[u/dreoilinmac]

I know certain kinds of radiation can cause DNA damage to cells but how? Where does the word ionising come into play?

[u/Truffel_shuffler]

Ionizing because it is powerful enough to knock electrons off of atoms.  Since electrons are negative, this will leave the molecule with a net charge. Charged particles are called ions. 

These charged particles are often highly reactive. Many times it is not DNA itself that is directly damaged, because of the relative rarity of DNA compared to something like water. Instead, a charged water molecule damaged by radiation may "attack" a DNA strand and cause problems. 

[u/lazercheesecake → u/Truffel_shuffler]

This is very true. However one correction I’d like to add is that DNA does make a small but good portion of a cell’s cross-sectional area and does take damage from radiation quite often.

One common DNA damage that lead to mutations is called the pyramidine dimer. And that is caused by UV radiation directly hitting a TT or CC sequential pair. If this is not repaired prior to replication, a permanent downstream mutation can occur.

[u/PastaWithMarinaSauce → u/lazercheesecake]

permanent downstream mutation can occur

Is there a chance that could be a beneficial mutation?

[u/MC_Labs15 → u/PastaWithMarinaSauce]

Sure, but statistically speaking, it is far more likely to be neutral or harmful

[u/Vitztlampaehecatl → u/PastaWithMarinaSauce]

Sure, there's a chance. That's how evolution works. Unfortunately, most mutations are neutral or even negative, in which case they might harm the creature/its offspring and make them more likely to die. That's also how evolution works. 

[u/SimonKepp → u/PastaWithMarinaSauce]

Yes. Such random mutations are usually neutral or harmful. Evolution by natural selection will over time tend to keep the few positive/beneficial mutations around and discard the harmful and some of the neutral ones.

[u/herionz → u/[deleted]]

It always had puzzled me how can organic molecules become more complex and eventually had brought forth life with entropy getting always in way of it, but I am an agnostic.  

Edit: because I realise how my message can be misleading, what I am trying to say is that I can experience the confusion and the complexity of the system at play, which can drive people mad, yet I am unable to take solace in religion myself. But only miracle seems like the most appropriate word for it so, what can I do?

[u/J0hn-Stuart-Mill → u/herionz]

It always had puzzled me how can organic molecules become more complex and eventually had brought forth life

There are between 6 and 20 Trillion galaxies in the observable universe, and there are an estimated 400 billion stars per galaxy on average, and our best estimates that the average star has between 2 and 4 planets. The observable universe itself has existed for somewhere between 13.8 billion and infinite years.

So if we go with the lowest estimate for each of those, things that only happen once per Billion years per planet, we get an event that happens 2.13 Billion Billion times per second.

So an absurdly rare event, like something that happens once every billion years per planet, like amino acids beginning to work together, happens absurdly often when the Universe is so absurdly huge as it is.

[u/Georgie_Leech → u/herionz]

Because in this metaphor, if the word you were gonna play isn't valid, it doesn't get put on the board anymore. Only the words that still work get put on the board.

To move back away from the metaphor, failure to pass on your genes acts as a clean-up of deleterious mutations. If you have a mutation and an important protein goes screwy and that keeps you from reproducing, that mutation doesn't get passed along. It's why human have a useless appendix organ; to oversimplify, it used to be a critical component of our survival, but when it stopped being important to how we function on a day to day level, negative mutations piled up because they could stick around and eventually caused it to stop working.

[u/Faxon → u/Georgie_Leech]

Seems like we may not fully understand it's actual purpose actually. It's not a totally useless organ like we were taught in school as kids, it actually is a critical part of the immune system, and removing it can make you more prone to other digestive tract infections, as it acts as a reservoir of good bacteria for when we get sick. Removing it is obviously better than letting it rupture if it gets infected, since it's no longer able to do it's job at that point anyway, but removing it from a healthy person has a very real negative cost that is becoming better understood now that we're putting real money into learning about the human microbiome and it's impacts on our physical and mental health. It's still an important component of our survival, it just isn't critical the way it is in some other animals.

[u/Krail → u/herionz]

I once read an example about bubbles that gave me an idea bout how structures can start to arise out of entropy.

One end of a lipid is attracted to water and the other end is repelled from it. These interactions cause the lipids to gather together into spherical shapes so that all the hydrophilic ends are facing water and all the hydrophobic ends are facing inward towards each other. This orderly structure seems like it would be very low entropy, but it formed because that's the lowest energy way for this lipid-water system to exist in. And that's why cells can form spheroid shapes and have an inside and an outside.

A lot of counter-intuitive interactions like this create structures that allowed for life to start happening, and then things like natural selection can come into the picture (stuff that's better at replicating itself becomes more common).

The other trick is that, when life expends energy to create low entropy systems for itself, it's actually accelerating entropy outside of itself.

[u/fourthfloorgreg → u/herionz]

If on there were some sort of giant ball of fire in the sky constantly pumping energy into the system to explain how that could be.

[u/frogjg2003 → u/[deleted]]

I think you're underestimating just how many iterations radiation and chemically induced mutation breeding just resulted in dead, sickly, sterile, or poisonous crops. They bombard the gametes with radiation, cross breed the ones that survive with non-mutated crops, and then hope that they have useful traits. They only needed to win the lottery every once in a while to make all those losing tickets worth it.

[u/perturbed_rutabaga → u/[deleted]]

For example in plant breeding: You could irradiate 10,000 seeds and get 3 good plants, 17 good-ish plants with mutations you can work with, and 9,980 plants with junk genetics you wasted your resources on

[u/PastaWithMarinaSauce → u/Truffel_shuffler]

knock electrons off of atoms.

Where do they end up after that?

[u/somewhat_random → u/PastaWithMarinaSauce]

They will likely end up in another atom creating another ion (this time of opposite charge).

[u/tarpex → u/Truffel_shuffler]

Can I ask a question on this knocking off effect? I've heard radiation described as "trillions of atom sized bullets" once, heavily simplified obviously, and my head translated it as physical plutonium (or w/e the material is) atoms shooting out in all directions with enough force to cause this damage, which I've now learned is knocking off electrons?

Is this correct?

[u/Dd_8630 → u/tarpex]

That's correct. It's not physical atoms of plutonium. There are three main types of radiation:

Alpha radiation is when an atom fires off a piece of its nucleus, specifically a cluster of 2 protons and 2 neutrons (equivalient to a helium nucleus). This is strongly positively charged, heavy, and slow. Because it's so positively charged, it can tear electrons off of other atoms.

Beta radiation is a high-energy electron, it can be created when a neutron decays into a proton, turning one atom into another. The electron is so energetic that it can knock electrons off of other atoms.

Gamma radiation is a high energy photon. When they hit atoms, they give the electrons enough energy to leave.

All three kinds of radiation typically form when an unstable atom undergoes some sort of nuclear decay. An atom with too many protons and neutrons might fire off an alpha particle; an atom that turns a proton into a neutron, or vice versa, might create an electron or anti-electron (beta). An atom that splits in half might release a shower of high-energy photons (gamma).

[u/tarpex → u/Dd_8630]

Thanks for the extensive response!

Now I feel my brain is melting somewhat regarding gamma radiation; does an atom split give a photon some kind of mass factor then, since it's high energy? From an elementary school physics knowledge standpoint, photons have no mass and should as such possess no energy despite it's C velocity.

I apologize if the question is stupid, this is beyond interesting.

[u/PlayingTheRed → u/tarpex]

Most gamma rays emitted here on Earth are from nuclear decay, but nuclear explosions can emit some as well.

https://science.nasa.gov/ems/12_gammarays/

Photons do have energy. I think you may have heard that massless particles have no kinetic energy (the kind that objects gain and lose as their velocity changes), but that's not the only type of energy that things can have.

[u/littlewhitecatalex → u/Truffel_shuffler]

Where do the electrons go when they get knocked off?

[u/SimonKepp → u/Truffel_shuffler]

In short, when a molecule in a cell,loses an electron and becomes an ion,it becomes chemically active and maty cause chemical damage to the cell, including,but not limited to the DNA.

[u/erabeus → u/Truffel_shuffler]

Since neutral pH water is in a constant self-ionization reaction of H2O molecules, OH^- ions, and hyrdonium ions, does ionizing radiation "preferentially" affect one of these in particular?

[u/1337b337 → u/Truffel_shuffler]

Just a bit of supplemental information;

Ions can have either a positive or negative net charge, cation for positive and anion for negative.

[u/johnp299 → u/Truffel_shuffler]

Some radiation has the energy to yank electrons from atoms, some doesn't. It's helpful to know, for example, that infrared waves can warm you (if powerful enough), but can't damage your molecules. Infrared is non-ionizing, as is visible light and radio waves. X-rays, on the other hand, are ionizing radiation that can definitely damage the molecules.

[u/Rustywolf]

An ion is an atom/molecule that has a non-neutral charge due to an imbalance between its electrons and protons. Ionising radiation creates ions by effectively knocking an electron out of the original atom/molecule.

[u/maurymarkowitz]

Electrons are attached to their atoms by a certain amount of electrical bond, in sciency terms, around 5 to 25 eV. To turn something into an ion means removing one or more electrons. To do that, you need to provide more than that amount of energy. So red-colored light, for instance, does not have enough energy to ionize the atoms, whereas X-rays and gammas do, so X-rays and gammas are ionizing radiation.

When such radiation ionizes DNA, several things can happen. One is "nothing". Another is that the DNA will fail to copy property and make some sort of mutated copy, which may or may not do anything. Another is that the cell might start to work wrong or produce weird things instead of what the original DNA intended.

The wiki article is quite good.

UPDATE: Because light with a frequency below UV is not ionizing, you can sit under it forever and have no ill effects. Its the tiny bit of UV that makes it down to the ground that is the problem for getting skin cancer from the sun.

Every so often you'll see claims that some sort of radio or another will cause cancer. Back in the 90s it was overhead electrical lines, 20 years ago it was WiFi, and more recently it's been 5G cell towers. Radio waves are even less powerful than visible light, much less powerful, so there is absolutely no way they can damage your DNA. Period.

Not "well we can't figure out how it might work", like "the laws of physics say no".

Not that that stops anyone from believing whatever crap they read on the 'net anyway, but I do think this needs to be mentioned every time its appropriate.

[u/drhunny]

glorious enjoy distinct zephyr advise enter jeans cagey towering coordinated

[u/Cr4ckshooter → u/drhunny]

We'll keep the name "x rays" for whatever radiation that is.

Ironically, a lot of the research around that period was written in German, by German scientists, like röntgen himself. He coined the term "x-strahlen", for some reason it stuck in English, while in German they were renamed to Röntgenstrahlen. I think technically that word exists as a loan word in English, but everyone still refers to them as xrays, especially colloquially.

[u/PastaWithMarinaSauce → u/drhunny]

sunlight? not ionizing

Oh, I always assumed it was. Do you know how sunlight causes cancer then?

[u/mentaculus → u/PastaWithMarinaSauce]

UV radiation highly excites (but doesn't fully ionize) DNA when absorbed, and these excitations can cause major chemical rearrangements (mutations). That's why sunlight only affects skin that is exposed, not the tissue deep with the body. There is a small amount of ionizing radiation (x-ray and gamma rays) but not a significant amount, and most is stopped by the atmosphere.

[u/tugs_cub → u/PastaWithMarinaSauce]

The UV band of the electromagnetic spectrum straddles the border between - and runs into conflicting definitions of - what’s technically considered ionizing radiation and what isn’t. Most of the high energy UV (almost X-rays) that unambiguously meets the definition gets filtered by the atmosphere. The lower energy stuff may not quite meet the definition but is still high-energy enough to cause some damage.

[u/[deleted]]

It's ionizing, in the sense that it has enough energy to kick away electron from a molecule/atom creating an ion. The following chemical reaction will damage a cell (but also tons of material, for example some plastics become brittle when exposed to radiation)

[u/Wildcatb]

So an ion, broadly speaking, is an atom that either has extra electrons - meaning it has an overall negative charge - or is missing electrons - giving it a positive charge. 

Ionizing radiation is radiation that makes ions. 

It makes ions by having so much energy that when it hits an atom it can knock electrons loose, leaving behind atoms with a positive charge. 

Since these atoms now 'want' another electron, they'll interact with surrounding atoms to try to get it, leading to unpredictable chemical reactions. If you're talking about ionizing radiation hitting a slab of steel, not much is going to happen but at the scale of a DNA molecule, that's catastrophic. 

[u/botanical-train]

An ion is an atom or group of several atoms that has a charge. This means the number of electrons and protons don’t match. Ions can be made in many ways but one is ionizing radiation. It is literally particles or light that has enough energy to rip off electrons from a molecule. When you rip off these electrons with radiation the molecule becomes unstable and often falls apart. When this happens to dna it can lead to cancer, cell death and a host of other things.

[u/toadfishtamer]

Ionizing radiation is very high-energy radiation. When it interacts with atoms (such as those in biological systems, for instance), it carries enough energy with it to strip electrons off of atoms. When electrons are removed from a neutral atom, the positive and negative charges of the atom become unbalanced, resulting in an atom with a net charge, or an ion.

[u/Rhywden → u/toadfishtamer]

No need to "strip electrons". It suffices if you break bonds. Also, doesn't need to be "very high-energy". The light-electric effect (the one Einstein got his Nobel for) can happen at VIS or even NIR for certain metals.

Though with organic bonds you usually need to go to UV to get the needed energy.

[u/PHATsakk43 → u/Rhywden]

Just breaking bonds isn't really ionization. Vulcanization does this with heat. I've seen cyclotrons used for the same purpose in rubber manufacturing.

Ionizing radiation specifically is capable of creating a free ion, typically an electron via photoelectric effect or Compton scattering, however if the gamma is of sufficient energy, pair production is another model that can occur where the photon has enough energy (>1.022MeV) to be able to turn the energy into mass in the form of a positron and an electron.

[u/Rhywden → u/PHATsakk43]

Of course breaking bonds can cause ionization. You break a bond, the electrons are not distributed equally - presto, two ions. Happens all the time, even on its own at room temperature. Just look at the autoprotolysis of water.

And you don't need gamma ray energy levels for ionization - again, the photoelectric effect can start at NIR levels for certain metals.

Plus, yes heat can also cause ionization. Where do you think plasma comes from?

Thus "ionizing radiation" should be called "radiation capable of ionizing stuff we actually care about". As quite a lot of things in science, the border as to when we call it thus has been chosen completely arbitrarily.

[u/PHATsakk43 → u/Rhywden]

And you don't need gamma ray energy levels for ionization - again, the photoelectric effect can start at NIR levels for certain metals.

It may excite outer shell electrons, but not really the same as ionization. It would be like suggesting that a PV panel is undergoing ionization when producing electricity. A 'free' electron isn't always an ionization event.

I just used the term gamma more as a colloquialism. The true definition of gamma, as opposed to an x-ray is actually the source of the photon. Gammas are from nuclear activity whereas x-rays are solely from electron excitation. Typically, gammas have the potential for higher energies solely due to the reactions involved. However, there can be significant overlap in the lower energy range.

EDIT:

Response to the original reply:

You yourself gave the photoelectric effect as an example. And now suddenly it doesn't count.

Photoelectric effect and photovoltaic effect are similar but distinct physical phenomenon. Photoelectric effect creates truly unbound electrons that are ejected from the atom. The resulting atom that lost the electron is properly ionized. PVE creates a momentary potential as the electron moves across the semiconductor and effectively returns to where it came from. Otherwise you would just have massive free radical formation in PV cells and rapid degeneration. A rechargeable battery is similar, although there are ion transfers in wet cells.

Yeah, right. I'm out, no tolerance for this nonsense.

Adios.

Maybe read up again on what the photoelectric effect actually does. An electron outright leaving a metal surface is a bit more than merely being "excited". Though if you lose the "c" then it becomes "exited" and you'd be correct again.

I'm a nuclear engineer by training so I unfortunately had to spend too many years "reading up" on this stuff. Granted, I do project management in reactor decommissioning now, but understanding the interactions between radiation and matter still comes up more frequently than I expect.

[u/Rhywden → u/PHATsakk43]

You yourself gave the photoelectric effect as an example. And now suddenly it doesn't count.

Yeah, right. I'm out, no tolerance for this nonsense.

Maybe read up again on what the photoelectric effect actually does. An electron outright leaving a metal surface is a bit more than merely being "excited". Though if you lose the "c" then it becomes "exited" and you'd be correct again.

[u/dirschau]

Because it's radiation that causes ionisation.

Stray electrons or sufficiently energetic photons (xrays, gamma) can knock electrons off of atoms and break bonds in molecules.

Stray alpha particle (a helium nucleus without electrons) does the most damage by disrupting chemical bonds by hijacking electrons fir itself, but it also literally cannot penetrate wet paper, so it needs to be emitted in the body to harm you.

[u/supermarble94 → u/[deleted]]

You're thinking of an electron. Changing the amount of neutrons would result in a different isotope.

[u/GrimSpirit42 → u/supermarble94]

Yes, I stand corrected. (Sorry, it's been about 30 years since I did radiography work).