Alpha Particle Mass

Alpha particles are alternatively known as Alpha radiation or Alpha rays. It is a positively charged particle emitted from the decay of various radioactive materials. Alpha particle mass is due to the two protons and two neutrons bonding. Thus, the Alpha ray nucleus is very similar to the Helium-4 nucleus. Represented by the Greek alphabet α. This article lets us know about alpha particle mass in detail, along with examples.

Table of Contents

Mass Of An Alpha Particle

An alpha particle can be called by an interchangeable term doubly ioniszed helium nuclei(He2+). The mass of an alpha particle is-

Alpha particle mass is αm = 6.644657230(82) × 10-27 Kg

Terms within the parenthesis represent the error factor.

Alpha Particle

Alpha particles are generally produced during standard radioactive decay. These alpha rays have an average kinetic energy of 5MeV and velocity in the vicinity of 5% of that of c. They are also produced in high energy particle accelerators. They are highly ionised particles and have low penetration depth. Generally stopped by a few centimetres of air or by the skin.

Some properties of an Alpha particle along with corresponding values and units are listed in the table below.

Alpha Particle Value
Alpha Particle mass in Kg 6.644657230(82) × 10-27 Kg
Mass of alpha particle in amu 4.001506179127(63) u
Mass of alpha particle in eV 3.727379378(23) GeV/c2
Alpha particle mass number 4
Alpha particle charge Positive
Alpha particle symbol α, &alpha2+, He2+.
Mass of alpha particle compared to proton Mass of alpha particle = 4 × mass of a proton

Alpha Particle Example

In general, any alpha decay can be given in the form –

\(\begin{array}{l}_{Z}^{A}\textrm{X}\rightarrow _{Z-2}^{A-4}\textrm{X’}+_{2}^{4}\textrm{He}\end{array} \)

Alpha particle example can be given as-

\(\begin{array}{l}_{238}^{92}\textrm{U}\rightarrow _{90}^{234}\textrm{Th}+_{2}^{4}\textrm{He}\end{array} \)


\(\begin{array}{l}_{2}^{4}\textrm{He}\,is\,the\,Alpha\,particle.\end{array} \)

Frequently Asked Questions – FAQs


How are alpha particles represented?

The Greek letter “α” is used to symbolise alpha particles.

What is an alpha particle?

A positively charged particle called an alpha particle is released during the radioactive disintegration of certain substances.

Does an alpha particle have mass?

Yes, the mass of an alpha particle is αm = 6.644657230(82) × 10-27 Kg

State true or false: The bonding of two protons and two neutrons accounts for the alpha particle’s mass.


State true or false: Alpha particles have a modest penetrating depth and are strongly ionised.


Physics Related Topics:

Proton Mass
Neutron Mass
Compton Wavelength
Deuteron Mass

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