Alpha, Beta and Gamma Rays (original) (raw)

Last Updated : 23 Jul, 2025

**Alpha, Beta, and Gamma Rays are types of rays that are radiated when particles or nuclei disintegrate. The nature of these three rays is different based on their composition. Alpha rays consist of two protons and two neutrons and have two positive charges. Beta Rays consist of electrons and have a negative charge while Gamma Rays consist of photons and are neutral.

In this article, we will learn what are alpha, beta, and gamma rays along with their properties, and comparison between them in tabular form.

Table of Content

• Alpha (α) Rays
• Beta (β) Rays
• Gamma (γ) Rays
• Properties of Alpha(α), Beta(β) and Gamma(γ) Rays

Alpha (α) Rays

An alpha particle is a helium nucleus (2He4) having two protons and two neutrons. The spontaneous emission of an alpha particle from a radioactive nucleus is called Alpha decay. α decay occurs when the nucleus emits α particles.

This process involves the spontaneous emission of nucleons since α particles (2He4) contain two protons and two neutrons therefore the emission of α particles causes the nucleus to get transmuted into a daughter nucleus having atomic number (Z) two less and atomic mass (A) four less.

Disintegration of a radioactive nucleus by emitting an α-particle as follows:

zXA → z-2Y A-4 + 2He4

(Parent nucleus) (Daughter nucleus) (α-particle)

Properties of Alpha Rays

• Alpha particles have charge +2e and mass 4u.
• Alpha particles have a kinetic energy of 5MeV.
• Nearly 90% of the 2500 known nuclides are radioactive. They are not stable but decay into other nuclides.
• When unstable nuclides decay into different nuclides, they usually emit alpha or beta particles.
• Alpha emission occurs principally with nuclei that are too large to be stable.
• Alpha decay is mainly governed by strong nuclear force and electromagnetic force.

Beta (β) Rays

A β-particle is a fast moving electron (e0). The spontaneous process of emission of beta particles from a radioactive nucleus is called Beta-decay.

The nucleus achieves greater stability in beta decay. In beta decay, either a neutron is converted into a proton or a proton is converted into a neutron.

The decay of a radioactive nucleus by emitting β-particle is represented as follows:

zXA → z+1YA + -1e0 + Ƴ

(Parent nucleus) (Daughter nucleus) (β-particle) (Antineutrins)

Beta-decay is mainly of three types: Beta-minus (β–), Beta-plus (β+), and electron capture.

Beta-Minus (β–)

• In beta-minus, the neutron inside the nucleus is converted into a proton and an electron like a particle.
• Those nuclei having more neutrons (N) than protons (Z) become unstable and tend to be beta-minus decay (β–).
• A β– particle is like an electron. The emission of β– involves the transformation of a neutron into a proton, an electron, and a third particle called Antineutrino.

**For Example:

**15 P 32 ⇢ **16 S 32 + **-1 e 0

Beta-plus (β+)

• In a β+ decay, a proton is converted into a neutron and a positron (-1e0 ) is emitted if a nucleus has more protons than neutrons.
• Nuclides for which N/Z is too small for stability can emit a positron, the electron’s antiparticle, which is identical to the electron but with a positive charge. The basic process is called beta-plus (β+) decay.

The process is represented as:

**p ⇢ n + β+ + v (v=neutrino)

Electron Capture

• Electron capture, nucleus absorbs one of the inner electrons revolving around it and hence a nuclear proton becomes a neutron and a neutrino (v) is emitted.
• Electron capture is compatible with a positron emission as both processes lead to the same nuclear transformation.

The process is represented as:

**1 H 1 + **-1 e 0 ⇢ **0 n 1 + v (v=neutrino)

Properties β Rays:

• β -particle has a negitive charge equal to the charge on an electron.
• They are deflected by electric and magnetic feilds.
• In a β decay, the neutron inside the nucleus changes into protons, as a result, the charge number remains the same, and the atomic number increases by one.
• In emission of β particle is accompanied by a companion particle having variable energy.
• The companion particle is massless and chargeless and is called Antineutrino.
• The emission of Antineutrino along with β particle conserves the angular momentum during β decay.
• The mass of neutrino and antineutrino is zero. The spin of both is 1/2 in units of h/2π. The charge on both is zero.
• The spin of neutrino is antiparallel to its momentum while that of antineutrino is parallel to its momentum.
• β particle can travel in air upto few metre.

Gamma (γ) Rays

γ-rays are the high energy packets of electromagnetic radiation i.e high energy photons.When the nucleus is placed in an excited state, either by bombardment with high energy particles or by a radioactive transformation, it can decay to the ground state by emission of one or more photons called gamma rays.

It is the spontaneous process of emission of high energy photons from a radioactive nucleus. The emission of alpha and beta particles leave the daughter nucleus in the excited state which in turn emits one or more Gamma-ray photons in single or successive transitions.

Since the gamma rays are emitted by the daughter nucleus emission of gamma rays for the emission of alpha and beta particles. The energy of gamma-ray is equal to the difference between the energy of the excited state or higher energy state and the ground state of the nucleons.

The Disintegration of a radioactive nucleus by emitting an γ-ray is represented as follows:

zXA* → zXA + γ

(Exicted Nucleus) (ground state) (Gamma particle)

Properties Gamma (γ) Decay:

• They have no charge.
• They are not deflected by electric and magnetic feilds.
• They affect the photographic plates
• The order of energy of Gamma Photon is 100 KeV.
• The rest mass of the Gamma Photon is zero.
• They have very high penetration power.
• gamma rays follows the emission of alpha or beta particle.

Properties of Alpha(α), Beta(β) and Gamma(γ) Rays

The difference between Alpha, Beta and Gamma Rays are tabulated below:

**Also, Check

• Radioactivity
• Types of Radioactivity
• Radiation