Beta Decay: Videos & Practice Problems

Beta decay is a nuclear process where an unstable nucleus emits a beta particle, which is a high-speed, high-energy electron. This decay occurs in nuclei with an excess number of neutrons and serves to reduce the neutron count while increasing the proton count, thereby achieving a more stable nucleus. During beta decay, a neutron is converted into a proton and an electron; the proton remains in the nucleus while the electron is ejected. For example, selenium-81 can transform into bromine-81 through beta decay, maintaining the mass number of 81 but increasing the atomic number by one. Beta particles, being smaller than alpha particles (helium-4 isotopes), have lower ionizing power but higher penetrating power, meaning they can pass through materials more easily. To shield against beta particles, denser materials like metal sheets or thick wood are required due to their higher penetrating ability. The characteristics of beta particles, including their size and ionizing and penetrating powers, are crucial to understanding their behavior and potential impact on biological tissue.

Beta Decay

Beta decay is a process that occurs in unstable atomic nuclei, where a beta particle, which is a high-energy, high-speed electron, is emitted. In terms of notation, an electron can be represented as either e or using the beta symbol β. Electrons are extremely light, with a mass number of 0 and a charge of -1, making them negligible compared to protons and neutrons.

This decay typically happens in nuclei that have an excess of neutrons. The primary goal of beta decay is to reduce the number of neutrons while increasing the number of protons, thereby achieving a more stable nuclear configuration. During this process, a neutron is transformed into a proton and an electron. The newly formed electron is ejected from the nucleus, while the proton remains within it.

For example, consider selenium-81 undergoing beta decay. The initial state has a mass number of 81 and 34 protons. After the decay, the mass number remains 81 since the emitted electron does not contribute to the mass. However, to maintain the same number of protons on both sides of the reaction, the atomic number must adjust. Since the original selenium has 34 protons, the product must have 34 protons as well. The emission of a beta particle (electron) effectively increases the atomic number by 1, leading to the formation of bromine-81, which has an atomic number of 35.

The overall beta decay reaction can be summarized as follows:

\[\text{Se}_{34}^{81} \rightarrow \text{Br}_{35}^{81} + \beta^{-}\]

This equation illustrates the transformation of selenium-81 into bromine-81 through the emission of a beta particle, highlighting the conservation of mass number and the adjustment of atomic number during the decay process.

Beta Decay Reaction Example

In the process of beta decay, iodine-129 undergoes a transformation that involves the emission of a beta particle, which is essentially an electron. Iodine, with an atomic number of 53, has a mass number of 129. During beta decay, a neutron in the iodine nucleus is converted into a proton, resulting in the emission of a beta particle (electron) and an increase in the atomic number by one.

The balanced nuclear reaction for the beta decay of iodine-129 can be represented as follows:

\[^{129}_{53}\text{I} \rightarrow ^{129}_{54}\text{Xe} + \beta^-\]

In this equation, the mass number remains unchanged at 129, while the atomic number increases from 53 (iodine) to 54 (xenon). This means that iodine-129 transforms into xenon-129 through the process of beta decay, while conserving both mass and charge in the reaction.

Characteristics of Beta Particles

Beta particles and alpha particles exhibit distinct characteristics that are crucial for understanding their behavior in various contexts, particularly in radiation and nuclear physics. Alpha particles, which consist of two protons and two neutrons, are relatively large and can be likened to helium nuclei. In contrast, beta particles are much smaller, essentially comprising a single electron.

One of the key differences between these two types of particles is their ionizing power. Alpha particles, due to their larger mass and slower movement, have a high ionizing power. When they interact with biological tissue, they can ionize surrounding atoms effectively because they move slowly enough to interact with multiple atoms. Conversely, beta particles, being lighter and faster, have a lower ionizing power. Their rapid movement allows them to traverse materials quickly, resulting in less time to ionize surrounding tissue.

In terms of penetrating power, beta particles outperform alpha particles. While alpha particles have limited penetrating ability due to their size and mass, beta particles can penetrate materials more effectively. For instance, alpha particles can be stopped by a sheet of paper, whereas beta particles require denser materials, such as a sheet of metal or a thick piece of wood, to be effectively shielded.

To illustrate these concepts with examples of radioactive decay, consider the decay of platinum-171, which undergoes alpha decay to form osmium-167. In contrast, selenium-81 undergoes beta decay to transform into bromine-81. This comparison highlights the differences in decay processes and the types of particles emitted.

In summary, the size and mass of alpha and beta particles significantly influence their ionizing and penetrating powers. Alpha particles, being larger, have high ionizing power but low penetrating power, while beta particles, being smaller and faster, exhibit lower ionizing power but higher penetrating power. Understanding these characteristics is essential for applications in radiation safety and nuclear science.

Characteristics of Beta Particles Example

Beta decay is a type of radioactive decay in which an unstable atomic nucleus transforms into a more stable one by emitting beta particles. These beta particles are high-energy, high-speed electrons or positrons that are ejected from the nucleus. One key characteristic of beta decay is that the emitted beta particles have a mass number of 0, as they are essentially electrons, represented as \( \frac{0}{-1} e \).While beta particles are indeed smaller in size compared to alpha particles, their ionizing power is lower. This is because, despite their high speed, they have less time to interact with and ionize the tissue they pass through. Consequently, beta particles can penetrate materials more effectively than alpha particles, but they cannot be stopped by skin alone; thicker materials, such as plastic or glass, are required for effective shielding.In summary, the characteristics of beta decay include the emission of high-energy electrons, a mass number of 0, and the need for thicker materials to block beta particles. The misconception that beta particles have higher ionizing power due to their speed is incorrect; in fact, their smaller size and speed result in lower ionization capability.

Here’s what students ask on this topic:

What is beta decay?

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Beta decay is a type of radioactive decay in which an unstable atomic nucleus transforms into a more stable one by emitting a beta particle. There are two types of beta decay: beta-minus (<sub>β<sup>-</sup></sub>) and beta-plus (<sub>β<sup>+</sup></sub>).

In beta-minus decay, a neutron in the nucleus is transformed into a proton, an electron (the beta particle), and an antineutrino. The electron and antineutrino are ejected from the nucleus, while the proton remains, resulting in an element that moves one place up the periodic table.

Beta-plus decay, also known as positron emission, occurs when a proton in the nucleus is converted into a neutron, a positron (the beta particle, which is the antimatter counterpart of the electron), and a neutrino. The positron and neutrino are emitted from the nucleus, and the element moves one place down the periodic table.

Both processes are mediated by the weak nuclear force, one of the four fundamental forces in physics. Beta decay changes the atomic number of the nucleus, thus transforming the original element into a different element, while the mass number remains unchanged.

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Which of the following describes radioactive decay by beta particle emission?

Radioactive decay by beta particle emission occurs when an unstable atomic nucleus transforms into a more stable nucleus by emitting a beta particle. There are two types of beta decay: beta-minus (₋) and beta-plus (₊).

In beta-minus decay, a neutron in the nucleus is transformed into a proton, and in the process, it emits an electron, known as a beta-minus particle, along with an antineutrino. The atomic number of the element increases by one due to the additional proton, but the mass number remains the same, resulting in the formation of a different element.

In beta-plus decay, also known as positron emission, a proton is converted into a neutron, releasing a positron, which is a beta-plus particle, and a neutrino. Here, the atomic number decreases by one, but again, the mass number does not change, leading to a different element.

Both processes are a way for the nucleus to achieve a more stable configuration of protons and neutrons.

Which of the following describes radioactive decay by beta particle emission?

Radioactive decay by beta particle emission occurs when an unstable atomic nucleus transforms into a more stable nucleus by emitting a beta particle. There are two types of beta decay: beta-minus (₋) and beta-plus (₊).

In beta-minus decay, a neutron in the nucleus is transformed into a proton, and in the process, it emits an electron, known as a beta-minus particle, along with an antineutrino. The atomic number of the element increases by one due to the additional proton, but the mass number remains the same, resulting in the formation of a different element.

In beta-plus decay, also known as positron emission, a proton is converted into a neutron, releasing a positron, which is a beta-plus particle, and a neutrino. Here, the atomic number decreases by one, but again, the mass number does not change, leading to a different element.

Both processes are a way for the nucleus to achieve a more stable configuration of protons and neutrons.

What happens in beta decay?

In beta decay, an unstable atomic nucleus transforms into a more stable nucleus by emitting a beta particle. There are two types of beta decay: beta-minus (β^-) and beta-plus (β⁺).

In beta-minus decay, a neutron in the nucleus is transformed into a proton, an electron (the beta particle), and an antineutrino. The emitted electron is ejected from the nucleus, while the antineutrino escapes with a portion of the energy. This process increases the atomic number of the element by one while keeping the mass number the same, effectively changing the element into its next neighbor on the periodic table.

In beta-plus decay, a proton is converted into a neutron, a positron (the beta particle), and a neutrino. The positron is the antimatter counterpart of the electron and is emitted from the nucleus along with the neutrino. This type of decay decreases the atomic number by one, turning the element into its previous neighbor on the periodic table.

Both types of beta decay are governed by the weak nuclear force, one of the four fundamental forces of nature, and they play a crucial role in the process of radioactive decay and the transmutation of elements.

What is ejected in a beta decay event?

In a beta decay event, there are two types of beta decay: beta-minus (₋) and beta-plus (₊).

In beta-minus decay, a neutron in an unstable atomic nucleus is transformed into a proton, and in the process, it emits an electron (also called a beta particle) and an antineutrino. The emitted electron is what is commonly referred to when talking about beta particles being ejected in beta decay.

In beta-plus decay, the reverse happens: a proton is converted into a neutron, and the nucleus emits a positron (the electron's antimatter counterpart) and a neutrino. The positron is the beta particle ejected in this type of decay.

Both of these processes result in the transformation of one element into another in the periodic table and are accompanied by the release of energy. These processes are examples of weak nuclear interactions and are important for understanding radioactive decay and the stability of atomic nuclei.