Problem 40 - Chemistry Matter and Change

Question

Colored Glass Thorium \(-230\) can be used to provide coloring in glass objects. One method of producing thorium- 230 is through the radioactive decay of actinium-230. Is this an example of alpha decay or beta decay? How do you know?

Step-by-Step Solution

Answer

This is a beta decay, as the atomic number increased by one.

Step 1: Identifying Actinium-230

To solve this problem, first identify the element Actinium (Ac) and its atomic number. Actinium has an atomic number of 89.

Step 2: Understanding Thorium-230

Recognize that Thorium (Th) is on the periodic table with an atomic number of 90. Therefore, thorium-230 has 90 protons.

Step 3: Analyzing the Change in Atomic Number

Since Actinium-230 has 89 protons and decays to Thorium-230 with 90 protons, there is an increase of 1 proton in the atomic number, from 89 to 90.

Step 4: Determining Type of Decay

In an alpha decay process, the parent nucleus loses 2 protons and 2 neutrons, reducing the atomic number by 2. In beta decay, a neutron converts to a proton, increasing the atomic number by 1 while mass number remains the same. Here, since the atomic number increases by 1, it indicates a beta decay.

Key Concepts

Alpha Decay

Alpha decay is a type of radioactive decay where an unstable nucleus transforms by emitting an alpha particle. An alpha particle is composed of 2 protons and 2 neutrons, identical to a helium nucleus. This process results in the original atom's atomic number decreasing by 2 and its mass number decreasing by 4.

For example, if a parent nucleus has an atomic number of 92, after alpha decay, the daughter nucleus will have an atomic number of 90. Here's the reaction:

• The original nucleus loses mass, thus resulting in a lighter, more stable nucleus.
• The release of an alpha particle can be stopped easily by a sheet of paper or human skin, indicating low penetration power but high ionizing power.

Alpha decay is commonly observed in heavy elements such as uranium, radium, and polonium.

Beta Decay

In beta decay, a neutron in an unstable nucleus is transformed into a proton and an electron. The electron, known as a beta particle, is emitted from the nucleus. As a result, the atomic number increases by one, while the mass number remains unchanged.

The process can be represented as:

• A neutron ( n ) is converted to a proton ( p ) and an electron ( e− ), which is the beta particle.
• The atomic number of the new element (daughter) is higher by 1 compared to the original element (parent).

Beta decay is stronger in penetration compared to alpha decay but can still be blocked by materials like aluminum.
In the exercise solution, you identified that Actinium-230 decays into Thorium-230 through beta decay due to an increase in atomic number by one. This confirms that one neutron in Actinium transformed, thus leading to this increase.

Actinium-230

Actinium is a radioactive element with the chemical symbol Ac and an atomic number of 89. Actinium-230 is an isotope of this element specifically. It is known for being part of a decay chain series, leading to other elements through radioactive decay.

Important points about Actinium-230 include:

• Being highly radioactive, Actinium isotopes, including Actinium-230, have limited applications outside of scientific research.
• The isotope has a limited half-life, meaning it decays relatively quickly compared to more stable isotopes.

In the context of the provided problem, we see Actinium-230 decaying into Thorium-230. This specific transformation involves beta decay as the atomic number increases by one.

Thorium-230

Thorium is a chemical element with the symbol Th and an atomic number of 90. Thorium-230 is a specific isotope of thorium, discovered as a product of decaying Actinium-230.

Key features of Thorium-230 are:

• It is part of the radioactive decay series, specifically known as the "uranium-238 decay series."
• Thorium-230 naturally occurs in minute quantities within the Earth’s crust but can be artificially generated, as noted in the glass coloring exercise.
• This isotope can emit radiation as it undergoes further decay, making it useful in certain scientific areas, despite its radioactivity.

Its decay characteristics make it less common for use than other stable thorium isotopes, yet its role in decay series highlights its importance in nuclear science. The transformation to Thorium-230 from Actinium-230 through beta decay exemplifies the complexity and fascinating nature of radioactive processes.