Problem 69 - Chemistry Matter and Change

Question

Smoke Detectors Americium-241, a radioisotope used in smoke detectors, is produced by bombarding plutonium- 238 with neutrons to produce plutonium-240, which is bombarded with neutrons to produce plutonium-241. The plutonium- 241 decays to americium-241. Write the balanced nuclear equations for each reaction.

Step-by-Step Solution

Answer

The balanced nuclear equations are: 1) \( ^{238}_{94}Pu + ^{1}_{0}n \rightarrow ^{240}_{94}Pu \); 2) \( ^{240}_{94}Pu + ^{1}_{0}n \rightarrow ^{241}_{94}Pu \); 3) \( ^{241}_{94}Pu \rightarrow ^{241}_{95}Am + ^{0}_{-1}e \).

Step 1: Understanding the Process

We need to write a series of nuclear equations that describe the transformation of plutonium-238 to americium-241 via various reactions. The first step involves bombarding plutonium-238 with neutrons to form plutonium-240.

Step 2: Reaction 1 - Plutonium-238 to Plutonium-240

In this reaction, plutonium-238 ( 238^{94}Pu) is bombarded with a neutron (
_0^1n), resulting in plutonium-240 ( 240^{94}Pu). The equation is:\[^{238}_{94}Pu + ^{1}_{0}n \rightarrow ^{240}_{94}Pu\]

Step 3: Reaction 2 - Plutonium-240 to Plutonium-241

Next, plutonium-240 is bombarded with a neutron, which leads to the formation of plutonium-241:\[^{240}_{94}Pu + ^{1}_{0}n \rightarrow ^{241}_{94}Pu\]

Step 4: Reaction 3 - Plutonium-241 Decay to Americium-241

Finally, plutonium-241 undergoes beta decay to become americium-241. In beta decay, a beta particle (
_0^{-1}e) is emitted:\[^{241}_{94}Pu \rightarrow ^{241}_{95}Am + ^{0}_{-1}e\]

Key Concepts

Americium-241

Americium-241 is a fascinating radioactive element often found in everyday devices such as smoke detectors. It acts as a key player in detecting smoke due to its ability to ionize air particles, allowing the detectors to pick up any change in electrical current. This change signals the presence of smoke, alerting us to danger.

Americium-241 is produced not by natural means but rather through a series of nuclear reactions. This element doesn't just appear out of thin air; it starts its journey from another element called plutonium-241. Through a process called beta decay, the transformation occurs, changing plutonium-241 into americium-241. Despite its radioactivity, americium-241 is safely used in smoke detectors due to its minimal and contained radiation levels, making it non-threatening to humans in this form.

• Commonly used in smoke detectors
• Produced from plutonium-241
• Involves the emission of beta particles

Plutonium-238

Plutonium-238 is an isotope of plutonium that plays a crucial role in the production of americium-241.

When plutonium-238 undergoes neutron bombardment, it first transforms into another isotope, plutonium-240. This reaction involves the capture of a neutron by the plutonium atom, which then increases its atomic mass number without changing its charge.
Plutonium-238 is not just vital in smoke detection applications. It's also used in space missions as a power source due to its long half-life and ability to generate heat. This is particularly beneficial for missions that travel far from the sun, where solar power is less effective.

• Undergoes neutron bombardment
• Transforms into plutonium-240
• Used as a power source in space exploration

Beta Decay

Beta decay is a type of radioactive decay where a beta particle, which is an electron, is emitted from an atomic nucleus. This fascinating process allows one element to transform into another.

In the case of plutonium-241 turning into americium-241, beta decay plays a pivotal role. During this decay, a neutron in the plutonium nucleus transforms into a proton, releasing a beta particle (electron) in the process.
This increase in the number of protons changes the element from plutonium to americium. The mass number stays the same since the neutron becomes a proton, changing the atomic number and thus altering its elemental identity.

• Involves emission of an electron (beta particle)
• Causes transformation from one element to another
• Maintains mass number, changes atomic number

Neutron Bombardment

Neutron bombardment is a process that involves firing neutrons at an atomic nucleus, which can change one element to another. It's like giving the nucleus new building blocks to reform itself.

In our scenario, neutron bombardment is used twice. First, it's used to change plutonium-238 into plutonium-240. Then, the same process transforms plutonium-240 into plutonium-241. Each time, the atom captures a neutron, increasing its mass number.
This process is critical in producing isotopes that don't naturally occur, like those used in medical and industrial applications. It's a fundamental technique utilized in science for creating elements and isotopes for various technological uses.

• Involves firing neutrons at atomic nuclei
• Used to produce new isotopes
• Essential in both scientific research and industrial applications