Alpha Particle Mass

Alpha particle is alternatively known as Alpha radiation or Alphay ray is a positively charged particle emitted from the decay of various radioactive material. Alpha particle mass is due to the two protons and two neutrons bonding. Thus, Alpha ray nucleus is very similar to the Helium-4 nucleus. Represented by Greek alphabet α.

Mass Of An Alpha Particle

An alpha particle can be called by interchangeable term doubly ionised 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 the highly ionised particles and have low penetration depth. Generally stopped by few centimetres of air or by the Skin.

Some of the property of Alpha particle along with corresponding value and units are listed in the table below.

Alpha Particle


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


Alpha particle charge


Alpha particle symbol

α, &alpha2+, He2+.

Mass of alpha particle compared to proton

Mass of alpha particle = 2 × mass of a proton

Alpha Particle Example

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

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

Alpha particle example can be given as-

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

Here, \(_{2}^{4}\textrm{He}\) is the Alpha particle.

Hope you have understood about alpha particle, how it is generated, its physical properties like – alpha particle mass, mass of alpha particle in amu, alpha particle charge, alpha particle symbol, alpha particle mass number, mass of alpha particle compared to proton. Along with alpha particle example and general form.

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