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What is an Alpha Particle?

Michael Anissimov
Updated May 21, 2024
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The alpha particle is a type of ionizing radiation. With its partners the gamma particles and beta particles, alpha particles are one of the most prevalent forms of radiation. Each particle is essentially a helium nucleus, which consists of two neutrons and two protons, without electrons, giving it a net positive charge. Due to their relatively high mass, these particles are the most destructive form of ionizing radiation, but the trade-off is that their penetration is low. A piece of paper stops alpha particles, whereas the lighter beta particles require a aluminum barrier.

Alpha particles are emitted from various radioactive substances. Unlike beta decay, alpha decay is mediated by the strong force. According to classical Newtonian laws, the attraction of the nucleus should be too strong to let alpha particles leave it under any circumstances. However, quantum tunneling permits it anyway. Quantum tunneling is the instantaneous teleporting of the particle to a place outside the nucleus.

Because alpha particles have such low penetrating force, they are stopped by human skin, presenting little danger unless the source is swallowed. This was the sad fate of Russian ex-spy Alexander Litvinenko, thought to be the first person to die from acute radiation poisoning as a result of ingesting the alpha emitter polonium. Other known alpha emitters include americium (found in smoke detectors), radium, radon gas, and uranium. When coupled together with certain other radioactive substances, alpha emitters can agitate neutron emitters to release the neutrons. Neutron emission is a critical part of nuclear reactor and nuclear weapons design.

In investigations into the health effects of smoking, it was found that tobacco leaves contain small amounts of polonium, which emits alpha particles. It is theorized that this could be partially responsible for lung cancer among smokers. In evolution, alpha emitters play a critical role — their likelihood of causing a chromosomal mutation is over 100 times greater than with other types of radiation. Most of the time, this produces less-fit mutants, but when combined with selection over thousands or millions of years results in adaptive biological designs.

All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Michael Anissimov
By Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology, astronomy, chemistry, and futurism to his articles. An avid blogger, Michael is deeply passionate about stem cell research, regenerative medicine, and life extension therapies. His professional experience includes work with the Methuselah Foundation, Singularity Institute for Artificial Intelligence, and Lifeboat Foundation, further showcasing his commitment to scientific advancement.
Discussion Comments
By anon311061 — On Dec 29, 2012

If an Alpha particle is a Helium nucleus, is it not easy to make it safe by adding two electrons to make the particle stable?

By anon151604 — On Feb 10, 2011

I understand a little more. Thanks for the post. -Michigan

By anon111200 — On Sep 15, 2010

Thank you tons for posting this. I understand much better now.I found this article to be interesting and pretty easy to understand.

By anon109323 — On Sep 07, 2010

thank you for your help. now i actually know its use. thanks very much.

By anon89623 — On Jun 11, 2010

I understand so much better now. Thank you.

By anon89408 — On Jun 10, 2010

Thank you. It helped a lot.

By anon89405 — On Jun 10, 2010

its kind of hard to understand. i think it needs to be explained more simply.

By anon85723 — On May 21, 2010

This is an amazing factual piece of work. it really helped me answer my school homework questions

By anon70398 — On Mar 14, 2010


By anon68541 — On Mar 03, 2010

I finally understand it. thanks wisegeek! very detailed and exactly what i wanted. From apawsey

By anon64328 — On Feb 06, 2010

So essentially an alpha particle is a messed up helium nucleus?

By anon56712 — On Dec 16, 2009

can these particles ingested in water kill or cause cancers? and can these particles be generated in the waste pool of a nuclear plant?

By anon55371 — On Dec 07, 2009

Very good piece of work. Very detailed piece.

By anon52694 — On Nov 16, 2009


By anon52052 — On Nov 11, 2009

this is absolutely outstanding.

By anon45391 — On Sep 16, 2009

yay! thanks. i understand it now!

By anon39105 — On Jul 30, 2009

Thank you for your article on Alpha particles. I'm studying for a radiography degree and its helped me hugely. Thanks guys

By anon36756 — On Jul 14, 2009

Uhm... could this be explained really simply please? Kind of confusing... Thanks!

Michael Anissimov
Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology...
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