Question

Match the following: List-I (Series) 1\. thorium 2\. naptunium 3\. actinium 4\. uranium List-II (Particles emitted) (i) \(8 \alpha, 5 \beta\) (ii) \(8 \alpha, 6 \beta\) (iii) \(6 \alpha, 4 \beta\) (iv) \(7 \alpha, 4 \beta\) The correct matching is: 1 2 3 4 (a) (iii) (i) (iv) (ii) (b) (i) (ii) (iv) (iii) (c) (iii) (i) (ii) (iv) (d) (ii) (i) (iv) (iii)

Short answer

Option (a): 1-iii, 2-i, 3-iv, 4-ii.

Step-by-step solution

Identify Thorium's Emission

Thorium emits a series of particles as it decays, specifically in the decay of Thorium-232. It primarily emits 6 alpha particles and 4 beta particles in its series. Hence, Thorium corresponds to (iii) \(6 \alpha, 4 \beta\).

Identify Neptunium's Emission

Neptunium in the context of decay series refers mostly to Neptunium-237. It emits 7 alpha particles and 4 beta particles in its decay series. Thus, it matches with (iv) \(7 \alpha, 4 \beta\).

Identify Actinium's Emission

Actinium is part of the Actinium series, specifically Actinium-227. This series matches with the emission of 8 alpha particles and 5 beta particles, aligning with (i) \(8 \alpha, 5 \beta\).

Identify Uranium's Emission

Uranium, particularly Uranium-238, undergoes decay resulting in the emission of 8 alpha particles and 6 beta particles, which corresponds with (ii) \(8 \alpha, 6 \beta\).

Match Series to Emissions

Based on the identified emissions, match the decay series to the particle emissions: 1. Thorium - (iii) 2. Neptunium - (iv) 3. Actinium - (i) 4. Uranium - (ii). Compare this sequence with the options provided to find a match.

Key concepts

Thorium Decay Series

The thorium decay series is a chain of successive radioactive decays, starting with thorium-232. An essential component of this series is the emission of specific particles during decay events. As thorium transitions through different decay steps, it emits 6 alpha (b1) particles and 4 beta (b2) particles before reaching a stable isotope, namely lead-208.
To understand why alpha and beta particles are emitted, consider that alpha particles are helium nuclei and are relatively heavy, meaning they effectively reduce both the atomic mass and the number of protons in thorium nuclei. On the other hand, beta particles are high-energy, high-speed electrons or positrons, slightly altering the atomic number while typically leaving the mass number the same.
Key stages in Thorium Decay:

• Begins with Thorium-232
• Emits 6 alpha particles
• Emits 4 beta particles
• Ends as stable Lead-208

Neptunium Decay Series

Neptunium, specifically Neptunium-237, is not a naturally occurring isotope but one found in nuclear reactions. The neptunium decay series is an artificial series that involves the emission of 7 alpha (b1) particles and 4 beta (b2) particles, resulting in a stable bismuth isotope.
This series is less commonly discussed than other decay series and is not typically encountered in nature due to the synthetic origin of Neptunium-237. However, it has significant importance in nuclear science, partly because its decay process sheds light on low-probability decay paths.
Steps in Neptunium Decay:

• Starts as Neptunium-237
• Releases 7 alpha particles
• Releases 4 beta particles sequentially
• Culminates in stable Bismuth-209

This series illustrates more intricate interaction paths in nuclear decay.

Actinium Decay Series

The actinium decay series, starting with uranium-235, ends at a stable lead-207 isotope. Actinium-227 is a prominent isotope in this decay series. It denotes a series where the parent isotope primarily decays through the emission of 8 alpha particles and 5 beta particles.
This series is significant in the natural radioactive decay processes, serving as the bridge between multiple isotopes and prominent alpha emissions. Understanding the decay steps in the actinium series reveals insights into the transitions between elements as uranium-based isotopes lose mass and atomic numbers.
Critical points in Actinium Decay:

• Initiates from Uranium-235
• Emits 8 alpha particles
• Emits 5 beta particles variably
• Yields stable Lead-207

Uranium Decay Series

The uranium decay series involves the decay of uranium-238, one of the most abundant isotopes found in nature. The decay path results in the production of 8 alpha (b1) particles and 6 beta (b2) particles, eventually forming a stable lead-206 isotope.
Uranium-238 undergoes multiple transformations, passing through several radioactive daughter isotopes, each contributing to the release of alpha and beta particles. This series is central to our understanding of natural decay processes and highlights how long decay chains persist within geological time frames.
Important Steps in Uranium Decay:

• Begins with Uranium-238
• Passes through different isotopes, emitting 8 alpha particles
• Simultaneously, releases 6 beta particles sequentially
• Culminates in stable Lead-206

This series profoundly influences geological dating techniques, such as uranium-lead dating, due to the reliable half-lives of the isotopes involved.