Types of radioactive decay (alpha, beta, gamma)

Radioactive decay is a natural process by which an unstable atomic nucleus loses energy. It occurs when the nucleus emits particles or electromagnetic waves. In simple terms, we can think of it as a way in which atoms become more stable by getting rid of some of their energy. In this lesson, we will explore the three main types of radioactive decay: alpha, beta, and gamma decay.

Alpha decay

Alpha decay is a type of radioactive decay in which a heavy nucleus emits an alpha particle. An alpha particle consists of two protons and two neutrons, the same as a helium nucleus. This form of decay usually occurs in very heavy elements such as uranium, radium, or thorium.

    _Z^AX → _{Z-2}^{A-4}Y + _2^4He
    

Here's a classic example of uranium decay:

    _{92}^{238}U → _{90}^{234}Th + _2^4He
    

Explanation: In this reaction, the uranium-238 nucleus decays into a thorium-234 nucleus and an alpha particle. The thorium nucleus has two fewer protons and four fewer nucleons than the original uranium nucleus. As a result of this reaction, the uranium atom loses some of its mass, becomes a different element (thorium) and emits an alpha particle.

Visual example:

Alpha decay is important in a variety of fields, including nuclear energy and medicine. However, alpha particles cannot penetrate skin or paper because of their relatively large mass and charge. Thus, they are not usually harmful outside the body, but can be dangerous if alpha-emitting substances are swallowed or inhaled.

Beta decay

Beta decay is another type of radioactive decay, but instead of emitting an alpha particle, the nucleus emits a beta particle. The beta particle is either an electron or a positron (the positively charged counterpart of the electron).

We divide beta decay into two types: beta-minus (β^-) decay and beta-plus (β⁺) decay.

Beta-minus decay (β^-)

In beta-minus decay, a neutron turns into a proton, and an electron is emitted, along with an anti-neutrino. This decay changes the element into a different element because it results in an increased number of protons.

    _Z^AX → _{Z+1}^{A}Y + _{-1}^{0}e + ν̄
    

Here's an example using carbon-14:

    _{6}^{14}c → _{7}^{14}n + _{-1}^{0}e + ν̄
    

Explanation: In this reaction, the carbon-14 atom turns into a nitrogen-14 atom. The carbon atom emits an electron (beta particle) and an anti-neutrino. The number of protons increases by one, due to which carbon becomes nitrogen.

Beta-plus decay (β⁺)

In beta-plus decay, a proton turns into a neutron, releasing a positron and a neutrino. Like beta-minus decay, this process also changes the element by reducing the proton number.

    _Z^AX → _{Z-1}^{A}Y + _{1}^{0}e + ν
    

Example using fluorine:

    _{9}^{18}F → _{8}^{18}O + _{1}^{0}E + ν
    

Explanation: In this reaction, the fluorine-18 atom becomes an oxygen-18 atom. A positron (positive beta particle) and a neutrino are emitted during this transformation. The number of protons decreases by one, resulting in fluorine turning into oxygen.

Visual example:

Beta particles have a greater penetration power than alpha particles but are still not very penetrating. They can pass through paper but are often stopped by thin layers of metal or plastic. Beta decay is used in a variety of applications, such as medical tracers and research.

Gamma decay

Gamma decay is the release of gamma rays from a radioactive nucleus. Gamma rays are a type of electromagnetic radiation that has neither mass nor charge and, therefore, does not change the atomic number or mass number of an element. Instead, they carry away excess energy from the nucleus.

    _Z^AX* → _Z^AX + γ
    

Let's consider a common example using cobalt-60:

    _{27}^{60}Co* → _{27}^{60}Co + γ
    

Explanation: Cobalt-60, in the excited state, releases a gamma photon (gamma ray) and becomes a more stable form of cobalt-60. The nucleus remains the same element, with the same number of protons and neutrons.

Visual example:

Gamma rays have a much greater penetration power than alpha and beta particles. They can pass through many types of materials, including thick metals and concrete. This makes them suitable for use in medicine, such as cancer treatment (gamma knife surgery), and also in industrial settings for inspection and diagnosis.

Summary

Radioactive decay plays a vital role in the stability of atoms and has practical applications in a variety of fields. Alpha decay involves the emission of helium nuclei, beta decay involves the emission of electrons or positrons, and gamma decay releases electromagnetic radiation. Each decay type has its own unique characteristics, uses, and safety considerations that need to be understood and respected.

Understanding the process of radioactive decay opens the door to knowledge about matter and energy transformations in the natural world.

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