Talk:Alpha decay
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[edit] I believe this is incorrect, please provide a reference
"Alpha decay is the most hazardous form of radiation,"
Gamma rays are more energetic, smaller, cross barriers better and are the most dangerous form of radioactivity from what I've read. No time to give references at the moment.--Voyajer 20:35, 19 January 2006 (UTC)
- Depends how you look at it. If you were exposed to equal amounts of alpha and gamma radiation, the alpha radiation would do you far more harm because gamma rays (like you said) cross barriers better - they go through you without doing much harm. Alpha particles are heavily ionising. The sense in which gamma rays can be called more harmful is that alpha particles are almost entirely obsorbed by a sheet of paper (it's actually how some smoke alarms work - smoke is denser and so blocks the alpha particles in the device), but gamma radiation will travel much further, doing only small amounts of damage over a long period of time. Here's a reference for you: [1]
- Alpha rays however, cannot pass through the skin, and must be inhaled or otherwise introduced into the body through another entrance. In this reference, you will see that it is described as not being able to pass through paper, but it is stopped by skin as well.[2] —Preceding unsigned comment added by 82.44.3.77 (talk) 18:34, 29 January 2008 (UTC)
[edit] Accuracy vs. Truthfulness
"Alpha decay is the most hazardous form of radiation,"
I've read it a few times, and, while the statement may be inaccurate (you can sit all day a foot away from an alpha emitter and never be hit by a single alpha particle), I'm not sure it's necessarily false...
The problem here is the definition of hazardous: alpha particles are big, slow-moving, and electrically charged, while gamma rays are tiny, electrically neutral, moving at the speed of light.
Therefore, a single gamma photon has a huge probability of going through a human body as if it didn't even exist (for the same reason why gamma ray shields are made from several inches of solid lead), while you can bet your house that, as long as it can reach the body, an alpha particle will hit the first layer of cells it meets and set up shop right there.
On the other hand, it must be noted that the first layer of skin cells is dead, so external exposition isn't usually cause for concern, and alpha particles are very short-lived in atmosphere, which makes even a few inches of air an effective shield against them.
On the gripping hand, if an alpha emitter (say, plutonium) enters the body, the released particles will happily run around, hunting for electrons.
Each of them needs two to turn into a stable, electrically neutral Helium atom, and we are talking about first-shell electrons here: I'd bet a pizza against an old shoe that alpha particles can strip electrons from a Fluorine atom, if that's all there is around.
If their speed is high enough, though, the electrons they strip from the surrounding atoms won't be able to bond with them: the alpha particle will slow down, but it will remain fully charged, and keep looking for electrons.
That gives them a huge ionizing potential - much more than gamma rays.
Whether that is enough to make them "the most hazardous form of radiation" is debatable... Maybe the article should just refer to the alpha particles page. -- * 2006-01-20 10:23 UTC
[edit] Accuracy?
The article says: "Alpha decay is the most hazardous form of radiation". Alpha decay IS NOT a form of radiation, it is a kind of radioactive decay. The forms of radiation are alpha particles, beta particles, gamma and X-rays etc. --V1adis1av 18:31, 20 January 2006 (UTC)
[edit] Charge?
I am in an introductory physics class and the question came up as to the charge of the daughter in an alpha decay reaction. We are curious why the equasion is not balanced with respect to charge since the alpha particle has a charge of +2. Can someone please explain this? --Forcemasteryoda
- Charge is balanced. (A,Z) -> (A-4,Z-2) + (4,2), i.e. the mother nucleus -> the daughter nucleus + alpha. Z is the charge, A - mass number.
I'm clearly missing something. Aren't there 2 more electrons on the left side and the right??
- No need to have electrons at all. These nuclei can even be naked (totally ionized). But in the case of neutral atom on the left side (Z electrons, Z protons), we have on the right side two atoms with Z-2 electrons in the daughter atom and 2 electrons in the helium atom (alpha particle). Really, the alpha is naked when emitted, but it gets two electrons from media when stops, and the (A-4, Z-2) atom gives to media two excess electrons and becames neutral again. --V1adis1av 13:33, 11 April 2006 (UTC)
Thank you for your help. --forcemasteryoda
Hi i have a similiar question: For the first equation, there is no charge on uranium, so it is taken to be a neutral atom. After an alpha-decay, shouldn't the thorium be written with a 2- charge? —Preceding unsigned comment added by 220.255.23.69 (talk • contribs)
- Hmmm... perhaps it would be less confusing if we wrote it with the electrons:
- after all if this is the decay of a neutral atom as you say, they must go somewhere. These aren't likely to matter much to a nuclear physicist, however, as they are not part of the nuclear reaction and won't leave the thorium with much energy (I suppose you might say they just drift away ... at least compared to the alpha). She is more likely to think of these as fully ionized or "naked" nuclei (no electrons at all):
- in which case the equation is obviously balanced! The reason the charge is emphasized on the helium is due to the fact that alpha particles are always emitted as "naked" nuclei. In other words, since the equation is intended to represent a nuclear reaction, atomic electrons are ignored. Hope this helps to clarify. -MrFizyx 16:56, 2 August 2006 (UTC)
Nice! Thanks for your help :)
[edit] Change to SI units
Shouldn't the speed of alpha particles be in m/s not km/s also it should be stated as the velocity of alpha particles and not the 'speed' 23:22 26 November 2006
Good point; actually it should provide context, i.e. that typical velocity of emitted alpha particle is about 5% of the speed of light (Lachlan, 31/1/07).
- "speed" would actually be the correct term as "velocity" is defined as "speed" in a certain direction. Starkrm 14:19, 28 March 2007 (UTC)
[edit] What causes it
The article is kind of confusing in the sense that the top part says it is caused by the electromagnetic force, and lower down it says it's governed by the stong nuclear force. Could it be both? AstroHurricane001 00:03, 6 December 2006 (UTC)
It is sort of both; an alpha emitter has too many protons & neutrons in the nucleus. The strong nuclear force is unable to completely overcome the repulsion between the protons caused by the electromagnetic force. Given protons always repel electrostatically, the strong nuclear force is considered inadquate to prevent this, so in that regard, it IS governed by the strong nuclear force. Hope this helps. Lokster 21:55, 14 February 2007 (UTC)
Is there any understanding of why this decay always produces helium nuclei, and not, say, deuterium or lithium?
[edit] Energy vs Half life
I think it would be worth mentioning that (in general) a higher decay energy corresponds to a shorter half life while a lower decay energy corresponds to a longer half life. Again, not always true, but a little more detail in this article would be handy. Anyone agree? (Lachlan, 31/1/07). —The preceding unsigned comment was added by 128.250.54.27 (talk) 01:13, 31 January 2007 (UTC).
[edit] toxicity section correction proposed
In the toxicity section, the first sentence does not make much sense and is false according to any decent radioactivity reference), and confuses the following statements. It has also been the cause of a lot of partial or false quotations above. I propose the following change to it (changes in caps):
"RADIOACTIVE NUCLEI THAT EMIT ALPHA PARTICLES are among the most hazardous SOURCES of radiation if these nuclei are incorporated within a human body. As any heavy charged particle, alpha particles lose their energy within a very short distance in dense media, causing significant damage to surrounding biomolecules. On the other hand, external alpha RADIATION is not harmful because alpha particles are completely absorbed by a very thin (micrometers) dead layer of skin as well as by a few centimeters of air. However, if a substance radiating alpha particles is ingested, inhaled by, injected into, or introduced through some skin-penetrating object (shrapnel, corrosive chemicals) into an organism it may become a risk, potentially inflicting very serious damage to the organism's genetic MATERIAL."
The main reason for confusion is that alpha-emitters typically also emit gamma radiation. More fact-checking and improvement for this page is definitely necessary. —The preceding unsigned comment was added by 129.2.40.128 (talk) 18:04, 1 February 2007 (UTC).
[edit] wikibug or something similar
With IE 7 on the alpha decay site I see only the following: " Edie Denvir-"Generic blackman, please stop raping me every day at school" Generic blackman-"No bitch, now suck my dick " But with firefox it shows the whole page? Weird. 87.94.138.102 20:27, 1 February 2007 (UTC)
