Alpha Particle Mass

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 its 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.

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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 proves 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 to that of the gamma rays. 

  • Despite having a large size and low perforating power, alpha radiations 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 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 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 the 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 the static electricity in industries. What happens in this method is, alpha particles attract free electrons towards itself; thereby, reducing the potential of the static electricity.

  • Pacemaker Battery

We can increase the life of a battery by using alpha radiations 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 life-span 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.

FAQs (Frequently Asked Questions)

Question 1: How Alpha Particles can be Dangerous?

Answer: Alpha particles can be dangerous in the following ways:

  1. 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.

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

Question 2: What is the Speed of an Alpha Particle?

Answer: 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 10ions along its path before it gains two e-to become a neutral He-atom.

Question 3: What is Americium-241? State the Uses of Americium.

Answer: 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.

  • Spectroscopy

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

  • Radiography

Question 4: How Do Alpha Particles Lose Energy?

Answer: 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.