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Alpha Particle Mass

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Last updated date: 23rd Jul 2024
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What is an Alpha Particle?

Radiation is one of the forms of energy that occurs when an unstable parent nucleus undergoes radioactive decay. Radiations travel a certain distance from their source in the form of energized waves/particles. The particles are alpha, beta, and gamma; these particles have different attributes and effects. We will focus on the alpha particle. Now, let’s understand what alpha particles are.

Alpha particles were named after the Greek alphabet ‘α’. The symbol for the alpha particle is α or α²⁺. As these particles are congruent to Helium nuclei. That’s why alpha particles can be written as He²⁺ or 24He indicating a Helium ion with a +2 charge (lacking two electrons). 

Alpha particles are known as α-rays or alpha radiation; these particles comprise two protons and two neutrons bound together into a particle isotropic to Helium-4 nuclei. These particles are developed during the α-decay process.

(Image will be uploaded soon)

(Image will be uploaded soon)

In this article, we will learn about alpha particles. So, let us get started with its characteristics.

Characteristics of Alpha Particle



Charge of alpha particle




Alpha Particle Mass

Mass of alpha particle in GeV/c²

3.727379378(23) GeV/c²

Mass of alpha particle in kg

6.644657230(82) х 10⁻²⁷kg 

Mass of alpha particle in amu

4.001506179127(63) u


Two Protons

Two Neutrons


Highly active & energetic

Penetration Power


Ionization Power



In the order of 10⁷ m/s.

Fundamental Properties of Alpha Particles

  • Alpha particles carry double the positive charge of the proton, i.e., equal to the charge on the Helium nucleus.

  • The mass of an α-particle is four times the mass of a Hydrogen atom, i.e., equivalent to the mass of the Helium atom.

(The above two properties prove that an alpha particle is equal to the Helium atom which has lost its two orbital electrons or a doubly ionized Helium atom).

  • The velocity of alpha particles ranges between 1.4 х 10⁷ m/s to 2.1 х 10⁷ m/s, relying on the source emitting/radiating it.

  • Because of the large mass of alpha particles, the penetrating power of these particles is lesser. It is 1/10³ times the penetrating power of beta rays and 1/10⁵ times that of the gamma rays. 

  • Despite having a large size and low perforating power, alpha radiation can stop by a 0.02 cm thick aluminium sheet.

  • On being stopped, alpha particles give rise to heating effects. Though alpha particles have low perforating power, they can cause burns on the human body.

  • Because of their large mass and high-stepping speed, these particles have excessive ionizing efficiency. It means a single alpha particle can bring forth thousands of ions before being absorbed.

  • The distance an alpha particle travels in the air relies on the radioactive source creating it. At the normal pressure in air, the range of alpha particles deviates from 3 to 8 cm.

  • Alpha particles produce fluorescence in certain substances, like Barium-Platinocyanide and Zinc-Sulphide (ZnS).

  • Alpha particles fractionally affect the photographic plates.

  • Alpha particles are deflected by both electric & magnetic fields at smaller angles. 

  • Alpha particles are garbled while passing through thin metal foils. 

  • Most of the particles were disordered at small angles; however, a few of them deflected at an angle greater than the right angle.

Uses of Alpha Radiations

Alpha radiations are very popular in day-to-day applications. Some of its uses are:

  • For Treating Cancer Patients

We use alpha particles in cancer treatment. While treating the cancer patient, doctors use a technique called Unsealed Source Radiotherapy. This technique involves inserting alpha particles like Radium-226 in tiny amounts into cancerous masses. We use Radium-223 to treat bone cancer.

  • Static Eliminator

Static Eliminator is a common technique used in industries like paper mills. This technique helps eliminate static electricity in industries. What happens in this method is, alpha particles attract free electrons towards themselves; thereby, reducing the potential of the static electricity.

  • Pacemaker Battery

We can increase the life of a battery by using alpha radiation as the source of energy. Alpha radiations of Plutonium-238 serve as the best fuel source for heart pacemakers.

  • Oil Industries

Alpha particles are the best source of energy, especially in remote areas. Alpha radiations of Strontium-90 serve as the best source to increase the lifespan of batteries.

  • Smoke Detectors

Smoke detectors typically fall into the following two categories:

  1. Photoelectric smoke detector

  2. Ionization smoke chamber detector.

Ionization smoke chamber detectors are common household items that keep us safe by alerting smoke in our homes. These detectors use a small amount of isotope of Americium, i.e., Americium-241 as the source of alpha particles. 

Alpha radiations ionize the air molecules, allowing a small current to flow between electrodes. This current rings an alarm.


Thus after reading this write-up on alpha particles we have understood what alphas particles are, how they are generated, their properties and characteristics and their uses. It has also helped us understand how important alpha particles are from the application point of view.

As a Physics student who will be handling such devices in the future, one must remember these particles are radioactive and can be damaging to your health. Thus when dealing with alpha particles a lot of care is taken.

Also by Vedantu

Vedantu suggests you go ahead and learn about beta particles (formed during beta decay) and gamma decay which produces gamma particles. Vedantu can also help you understand the topic of applications of Radioactivity in detail.

FAQs on Alpha Particle Mass

1.What are Alpha Particle Mass – Definition, Characteristics, Properties and Uses?

Alpha Particle Mass – Definition, Characteristics, Properties and Uses can be defined as a radioactive particle that is made up of two protons and two neutrons. It is nothing but a helium nucleus i.e. a helium atom without electrons. They are formed by the process of radioactive decay where Radioactive elements give out alpha particles. This is the simplest explanation you can find for definitions of alpha particles. These particles have a wide range of applications. You can find more elaborate definitions of alpha particles and examples on Vedantu’s website.

2.What are the dangers associated with Alpha Particle Mass – Definition, Characteristics, Properties and Uses?

Alpha particles that are discussed in Alpha Particle Mass – Definition, Characteristics, Properties and Uses are very dangerous. They are easily absorbed by the cells. They cause more internal hazards as compared to beta obtained in beta decay and gamma particles. They can reach the internals of a human via  inhalation, swallowing, absorption or injection. They can damage sensitive living tissue present in our bodies. They can also damage the DNA and cause cancer if exposed for a prolonged period. Thus wherever research is going on which involves interaction with alpha particles a lot of precautionary measures are taken.

3.How much time does it take to cover Alpha Particle Mass – Definition, Characteristics, Properties and Uses?

It should not take more than 2 hours on average to read and understand the topic of Alpha Particle Mass – Definition, Characteristics, Properties and Uses from Vedantu's website. This will cover the topic holistically. But it won’t be sufficient. You need to read the same topic from Physics NCERT and solve problems on radioactive decay. To cover this topic for various entrance exams such as JEE and NEET you need to study and solve problems from the HC Verma’s books as well. Completing these exercises will prepare you to answer questions related to this topic in every exam. Try to solve a variety of problems to expose yourself to different levels of difficulty.

4.Can Vedantu’s Alpha Particle Mass – Definition, Characteristics, Properties and Uses help me in scoring full marks in Class 12 Physics board exams?

Yes studying Alpha Particle Mass – Definition, Characteristics, Properties and Uses can surely help you score very good marks in Class 12 Physics exams. Vedantu has covered each and every topic in great detail and in the process, nothing has been skipped. All the content is designed by Vedantu’s subject matter experts for you for free. These experts have been teaching physics for several years and are well aware of challenges faced by the students, thus they have ensured all the materials are extremely student-friendly. Thus studying these materials will not only simplify the topic but will help you fetch excellent marks in the exam.

5.What books do I need to study to cover Alpha Particle Mass – Definition, Characteristics, Properties and Uses holistically?

You can start by reading Alpha Particle Mass – Definition, Characteristics, Properties and Uses from Vedantu’s website. This can be a good start for you to understand the topic of alpha particles. Post this, you can read this topic from NCERT Class 12 Physics textbook. It will cover the entire topic in and out. It will also cover mathematical equations and derivations. We suggest you also solve all the problems and theory questions given at the back of the chapter. It will fully prepare for the Class 12 board exams. After this, proceed towards learning advanced level topics for your entrance exams from the HC Verma’s books. You can also refer to CBSE Class 12 Physics sample questions papers to understand what types of questions are to be expected and direct your preparation accordingly.

6.What are the properties of Alpha Particles?

Alpha particles have the following properties:

  • Their speed is slower than the other forms of nuclear radiation

  • They are heavier than other nuclear radiations

  •  They travel at the speed of 5 to 7 % of the speed of light or 20,000,000 metres per second

  • They have a mass equivalent to 4 protons 

  • They are not able to penetrate very far through matter because they are highly ionizing.

These properties are used in a wide variety of applications such as while carrying out experiments in labs and while carrying out reactions in nuclear reactors.

7.What are the applications of Alpha particles?

Alpha particles are used as alpha radiations in a wide variety of fields such as:

  • For cancer treatment:The alpha particles are inserted into the cancerous mass. The alpha particles destroy cancer cells 

  • For smoke detection:The alpha particles bombard the molecules present in the air and knock the electrons free. These electrons are then utilised for creating an electrical current. Smoke particles if present will disrupt this current and thereby trigger an alarm.

  • For powering spacecraft: In Spacecrafts, Plutonium-238 serves as the fuel source. This produces alpha radiation which results in heat, which is then converted to electricity.

  • In pacemaker batteries: Alpha radiation generated from alpha particles is used as a source of energy to power heart pacemakers.

In heating devices: For this purpose, radioisotopes are used.  Radioisotope generators directly use the heat generated by alpha decay reactions to power various heating devices.

8.What is the speed of Alpha Particles?

An alpha particle is heavier than other particles associated with nuclear radiation. Due to this, its velocity is comparatively slower. It travels at the speed of 5-7% of the speed of light that is 2,00,000 m/s. This is the natural speed of an alpha particle. But in labs using devices such as particle accelerators, one can modify this speed and take it up to a higher speed. Here one thing should be noted that alpha particles show lower speeds owing to their heavier mass as compared to other particles.

9.How Alpha Particles Can be Dangerous?

Alpha particles can be dangerous in the following ways:

Alpha particles are helpful in cancer treatment. Proper care is to be taken while injecting alpha emitters through the cut. If these rays enter the neighboring organs of the body, they can damage them.

Emission of alpha radiation from nuclear power plants can enter the DNA, damage the cells, and cause cancer.

10.What is the Speed of an Alpha Particle?

An alpha particle can travel 5-7% of the speed of light, i.e.,  2,00,000 meters per second. An individual alpha particle, when ejected from a nucleus, can create up to 105 ions along its path before it gains two e-to become a neutral He-atom.

11.What is Americium-241? State the Uses of Americium.

Americium-241 is one of the most common isotopes of Americium with a half-life of 432.2 years. The following are its uses: 

On blending Americium with Beryllium, we can use this mixture as a neutron source in the testing of machinery in industries.


Americium can be used to create flat glass by estimating its thickness.


12.How Do Alpha Particles Lose Energy?

Alpha particles are capable of attracting electrons from huge distances. After pulling electrons from atoms, they ionize atoms. 

Alpha particles consecutively lose energy, slow down, finally stop and turn to a neutral He-atom.