Beta and Gamma Decay

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Beta and Gamma Decay

This lesson aligns with NGSS PS4.B

Introduction

Nuclear decay is a fascinating phenomenon that occurs in unstable atomic nuclei as they seek stability by releasing energy in various forms. Among the different types of radioactive decay processes, beta decay and gamma decay are two important mechanisms through which nuclei achieve a more stable state..In this article, we will explore the fundamental principles, differences, and applications of beta and gamma decay.

1. What is Beta Decay?

Beta decay is a type of radioactive decay in which an unstable nucleus transforms into a more stable one by emitting a beta particle. The term "beta" refers to the high-energy, high-speed particles that are emitted during the decay process. There are two types of beta particles: beta-minus (

$beta^-$ ) particles, which are electrons, and beta-plus (

$beta^+$ ) particles, which are positrons (the antimatter counterpart of electrons).

The process of beta decay occurs when the neutron-to-proton ratio in a nucleus is imbalanced. A nucleus with too many neutrons relative to protons undergoes beta-minus decay, while a nucleus with too few neutrons undergoes beta-plus decay. Let’s examine each type of beta decay in more detail.

Beta-Minus Decay (

$beta^-$ Decay)

In beta-minus decay, a neutron inside the nucleus is transformed into a proton, an electron, and an antineutrino. The electron, or beta-minus particle, is then ejected from the nucleus at a very high speed. The basic equation for beta-minus decay can be represented as:

In this equation:

n represents a neutron.
$P^+$ is a proton.
$e^-$ is the beta-minus particle (an electron).
$hat v_e$ is an electron antineutrino.

This process increases the proton count in the nucleus, turning the element into a different one with a higher atomic number. For example, carbon-14 (with 6 protons and 8 neutrons) undergoes beta-minus decay to become nitrogen-14 (with 7 protons and 7 neutrons).

Beta-Plus Decay (

$beta^+$ Decay)

Beta-plus decay occurs when a proton in the nucleus is transformed into a neutron, a positron, and a neutrino. The positron,which is the beta-plus particle, is expelled from the nucleus. The basic equation for beta-plus decay is:

In this equation:

$p^+$ represents a proton.
n is a neutron.
$e^+$ is the beta-plus particle (a positron).
$v_e$ is a neutrino.

Beta-plus decay decreases the proton count in the nucleus, leading to the formation of an element with a lower atomic number. For example, a proton-rich isotope like carbon-11 undergoes beta-plus decay to become boron-11.

2. What is Gamma Decay?

Gamma decay is different from beta decay in that it involves the emission of electromagnetic radiation (photons) rather than particles. When a nucleus undergoes alpha or beta decay, it often ends up in an excited energy state. In order to shed this excess energy and return to its ground state, the nucleus emits gamma rays. Gamma rays are high-energy photons with no mass and no charge, making them a form of ionizing radiation.

The process of gamma decay can be represented simply as:

Here:

$X^*$ represents an excited nucleus.
X is the nucleus in its ground state.
$gamma$ represents the emitted gamma photon.

Because gamma decay involves no change in the number of protons or neutrons, the element itself does not change. Instead, it just loses energy. For example, when cobalt-60 undergoes beta decay, it leaves the daughter nucleus (nickel-60) in an excited state, which then emits gamma rays to stabilize.

3. Differences Between Beta and Gamma Decay

While both beta and gamma decay are methods by which unstable nuclei attain stability, they differ in several key aspects:

Type of Emission: In beta decay, particles (electrons or positrons) are emitted, while gamma decay emits photons (gamma rays).
Change in Atomic Number: Beta decay changes the atomic number of the element, transforming it into another element. In contrast, gamma decay does not alter the atomic number or mass; it simply reduces the energy of the nucleus.
Penetration Power: Gamma rays are highly penetrating and can travel through several centimeters of lead or meters of concrete, whereas beta particles are less penetrating and can be stopped by materials like plastic or glass.
Energy Release: Beta decay releases both kinetic energy (due to the ejected beta particles) and energy in the form of radiation, whereas gamma decay releases energy solely in the form of electromagnetic radiation.

Conclusion

Beta decay is a type of radioactive decay in which an unstable nucleus transforms into a more stable one by emitting a beta particle.
The term "beta" refers to the high-energy, high-speed particles that are emitted during the decay process.
Gamma decay is different from beta decay in that it involves the emission of electromagnetic radiation (photons) rather than particles.
When a nucleus undergoes alpha or beta decay, it often ends up in an excited energy state.
In order to shed this excess energy and return to its ground state, the nucleus emits gamma rays.

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