21.2 Radioactive Decay

Summary

This video covers the topic of radioactive decay, explaining the spontaneous breakdown of unstable atomic nuclei into smaller nuclei while emitting radiation. It explores five main types of decay: alpha, beta, positron emission, electron capture, and gamma ray emission. The concept of half-life is discussed, highlighting how long it takes for half of a radioactive sample to decay. The video also delves into decay series, using uranium-238 as an example of a sequence of decays until a stable nucleus is reached. Lastly, it touches on artificial transmutation, which is used to create new elements in particle accelerators.

Takeaways

• 😀 Radioactive decay is the spontaneous disintegration of a nucleus into smaller nuclei, releasing radiation such as particles or electromagnetic rays.
• 😀 Alpha decay involves the emission of a helium nucleus (two protons and two neutrons) from a larger nucleus, resulting in a new element.
• 😀 Beta decay occurs when a neutron decays into a proton and an electron, typically when there are too many neutrons in a nucleus.
• 😀 Positron emission is the release of a positron (the anti-particle of an electron) when there are too many protons in the nucleus, resulting in a neutron.
• 😀 Electron capture happens when a nucleus absorbs one of its inner-shell electrons, transforming a proton into a neutron.
• 😀 Gamma rays are high-energy electromagnetic radiation emitted during radioactive decay, usually following the decay of alpha or beta particles.
• 😀 Half-life refers to the time it takes for half of a sample of a radioactive isotope to decay, indicating its stability over time.
• 😀 Longer half-lives signify more stable isotopes, while shorter half-lives indicate rapid decay and higher emissions.
• 😀 A decay series is the sequence of radioactive decays that a nucleus undergoes, eventually reaching a stable form.
• 😀 Uranium-238, for example, undergoes a series of decays until it stabilizes as lead-206, with each decay involving the emission of different particles.
• 😀 Artificial transmutation is the process of creating new elements by accelerating smaller nuclei to collide with larger ones, as seen in particle accelerators.

Q & A

What is radioactive decay?

Radioactive decay is the spontaneous disintegration of an unstable nucleus into smaller nuclei, accompanied by the emission of particles or electromagnetic radiation, such as alpha particles, beta particles, or gamma rays.

What types of radiation are emitted during radioactive decay?

During radioactive decay, radiation can be emitted as particles (alpha, beta, positron) or electromagnetic waves (gamma rays).

What is the difference between alpha decay and beta decay?

Alpha decay involves the emission of a helium nucleus (2 protons and 2 neutrons), whereas beta decay involves the emission of an electron from the nucleus, resulting from the transformation of a neutron into a proton.

How does positron emission work?

Positron emission occurs when an atom with too many protons undergoes decay by emitting a positron, which is the antiparticle of an electron. The proton is converted into a neutron to stabilize the nucleus.

What is electron capture?

Electron capture occurs when a nucleus absorbs one of its inner-shell electrons, causing a proton to combine with the electron and form a neutron.

What are gamma rays and how do they relate to radioactive decay?

Gamma rays are high-energy electromagnetic radiation emitted from a nucleus, often following other types of radioactive decay. They are some of the highest-energy photons in existence.

What does 'half-life' mean in the context of radioactive decay?

Half-life refers to the time it takes for half of a sample of a radioactive isotope to decay. It provides a measure of the stability of the isotope, with a longer half-life indicating more stability.

How does the decay series of uranium-238 work?

The decay series of uranium-238 involves a series of radioactive decays, starting from uranium-238 and ultimately ending in stable lead-206, with intermediate nuclides such as thorium, radium, and others. Each step involves the emission of particles, such as alpha or beta particles.

What is meant by 'parent nuclide' and 'daughter nuclide' in a decay series?

In a decay series, the 'parent nuclide' is the original and heaviest nuclide that undergoes decay, while the 'daughter nuclides' are the nuclides produced as a result of the decay process.

What is artificial transmutation and how is it used?

Artificial transmutation is the process of creating new elements by accelerating smaller nuclei and colliding them with larger nuclei. This process is commonly used in particle accelerators to create elements beyond uranium, such as plutonium and americium.