What are alpha particles?

Alpha Particle.

alpha particle, positively charged particle, identical to the nucleus of the helium-4 atom, spontaneously emitted by some radioactive substances, consisting of two protons and two neutrons bound together, thus having a mass of four units and a positive charge of two. Discovered and named (1899) by Ernest Rutherford, alpha particles were used by him and coworkers in experiments to probe the structure of atoms in thin metallic foils. This work resulted in the first concept of the atom as a tiny planetary system with negatively charged particles (electrons) orbiting around a positively charged nucleus (1909–11). Later, Patrick Blackett bombarded nitrogen with alpha particles, changing it to oxygen, in the first artificially produced nuclear transmutation (1925). Today, alpha particles are produced for use as projectiles in nuclear research by ionization—i.e., by stripping both electrons from helium atoms—and then accelerating the now positively charged particle to high energies.

What are the properties of alpha particles?

Alpha particles are relatively slow and heavy compared with other forms of nuclear radiation. The particles travel at 5 to 7 % of the speed of light or 20,000,000 metres per second and has a mass approximately equivalent to 4 protons.

Alpha particles, because they are highly ionising, are unable to penetrate very far through matter and are brought to rest by a few centimetres of air or less than a tenth of a millimetre of biological tissue.

What are the health effects of exposure to alpha particles?

Alpha particles are highly ionising because of their double positive charge, large mass (compared to a beta particle) and because they are relatively slow. They can cause multiple ionisations within a very small distance. This gives them the potential to do much more biological damage for the same amount of deposited energy.

Alpha particles can’t penetrate the normal layer of dead cells on the outside of our skin but can damage the cornea of the eye. Alpha-particle radiation is normally only a safety concern if the radioactive decay occurs from an atom that is already inside the body or a cell. Alpha-particle emitters are particularly dangerous if inhaled, ingested, or if they enter a wound.

What are some common sources of alpha particles?

Many alpha emitters occur naturally in the environment. For example, alpha particles are given off by radionuclides such as uranium-238, radium-226, and other members of the naturally occurring uranium, thorium and actinium decay series which are present in varying amounts in nearly all rocks, soils, and water.

Artificially produced sources of alpha particles include the radioisotopes of elements such as plutonium, americium, curium and californium. These are generally produced in a nuclear reactor through the absorption of neutrons by various uranium radioisotopes.

What are some uses of alpha particles?

Alpha particles have low penetrating power but this still provides a range of useful applications:

▪️smoke detectors – americium-241 is commonly used in ionising smoke detectors. Smoke that enters the detector reduces the amount of alpha particles that are detected and triggers the alarm.

▪️static eliminators typically use alpha particles from polonium-210 to remove static charges from equipment.

▪️radioisotope thermoelectric generators use alpha particle decay from plutonium-238 to generate heat which is converted to electricity, commonly used in space probes .

▪️some alpha emitters are being investigated for their potential use in unsealed source radiotherapy to treat cancer.

▪️Pacemaker battery. Alpha rays of plutonium-238 are used in pacemaker batteries as a power source, and have a life span of up to 88 years, and this helps to save energy for a long time, but it is no longer used now because of its toxicity, and it is difficult to use while traveling .

▪️Remote sensing stations. There are countries that use alpha rays of strontium-90 as a fuel source to operate remote sensing stations, such as the United States of America, which uses alpha rays to power remote sensing stations in Alaska.

▪️Heating devices. Alpha rays decompose and produce heat. This heat is used for heating on spacecraft, and this use of alpha rays is one of the most important uses for astronauts.

▪️Coastal protection buoys. Alpha rays of strontium-90 are used to power ocean buoys, and alpha batteries have a long life and have already been used by the US Coast Guard.

▪️Oil Well Equipment. Alpha rays of strontium-90 are used to power offshore equipment used to extract oil from the sea.

▪️Seismic and oceanic instruments. Alpha rays of strontium-90 are used to power many seismographs and other oceanic instruments, and these instruments are often placed in isolated places, such as ocean floors.


The Editors of Encyclopædia Britannica, “Alpha particle”،”

Alpha particles”,

ما هي أشعة ألفا ؟/

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button