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Physics 001.002.015 Artificial Transmutation

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Physics 001.002.015 Artificial Transmutation

Alignment

Learning Intentions

By the end of the lesson, students will be able to:

  • Describe artificial transmutation as a human-induced nuclear reaction that changes one nuclide into another.
  • Represent artificial transmutation using balanced nuclear equations.
  • Identify the role of bombarding particles such as neutrons, protons, alpha particles or other nuclei.
  • Distinguish artificial transmutation from natural radioactive decay.

Success Criteria

By the end of the lesson, students have successfully:

  • Stated that artificial transmutation occurs when a nucleus is deliberately changed by collision with another particle or nucleus.
  • Explained that the atomic number changes when the number of protons in the nucleus changes.
  • Balanced nuclear equations by conserving mass number and atomic number .
  • Described examples of artificial transmutation, including neutron capture and particle bombardment.
  • Compared artificial transmutation with spontaneous natural decay.

Syllabus Reference

  • Unit 1: Thermal, Nuclear and Electrical Physics
  • Topic 2: Ionising Radiation and Nuclear Reactions
  • Energy and Mass Defect
  • Describe the concept of artificial transmutation.
  • Distinguish between artificial transmutations and natural radioactive decay.

Phenomenon

In nature, some unstable nuclei decay spontaneously, but in laboratories, reactors and particle accelerators, scientists can force nuclear change to occur.

For example, a stable aluminium nucleus can be bombarded with an alpha particle to form a different nuclide:

The aluminium nucleus has been changed into phosphorus. This is artificial transmutation.

Key Idea

Artificial transmutation is the process of changing one nuclide into another by deliberately bombarding its nucleus with a particle or another nucleus.

Concept

The concept and thought that best describes the cause of the phenomenon is below.

A nucleus is made of protons and neutrons. The identity of an element is determined by its number of protons, called the atomic number .

Artificial transmutation occurs when an incoming particle collides with a target nucleus and causes a nuclear reaction. If the reaction changes the number of protons in the nucleus, the target atom becomes a different element.

A general artificial transmutation reaction can be written as:

where:

  • is the target nuclide
  • is the bombarding particle
  • is the product nuclide
  • is an emitted particle or radiation

Artificial transmutation is not a chemical reaction. It changes the nucleus, not just the arrangement of electrons.

Convention

The key conventions associated with the concept and in the branch of established knowledge is below.

Nuclear equations must conserve:

  • mass number
  • atomic number
  • charge
  • nucleon number

Common particles used in artificial transmutation include:

ParticleSymbolMass number Atomic number
Neutron
Proton
Alpha particle or
Electron / beta negative or
Positron / beta positive or
Gamma radiation

To check a nuclear equation:

For mass number:

For atomic number:

Example:

Mass number:

Atomic number:

Therefore, the nuclear equation is balanced.

Misconceptions

Common misconceptions students have regarding the concept when applying to various situations and solving problems. It could be a conceptual, mathematical or logical misconception.

  • Artificial transmutation is not the same as chemical change. Chemical reactions rearrange electrons, while artificial transmutation changes the nucleus.
  • Artificial rearrange electrons, while artificial transmutation changes the nucleus.
  • Artificial transmutation does not always produce a radioactive product. Some products may be stable, while others may be radioactive.
  • The mass number and atomic number are not always both changed in the same way. A neutron can change the mass number without directly changing atomic number.
  • Gamma radiation does not change the identity of a nuclide because it has and .
  • Natural radioactive decay is spontaneous, while artificial transmutation is deliberately induced by collision with another particle or nucleus.

Further Reading

  • Rutherford’s nitrogen transmutation experiment
  • Neutron activation in nuclear reactors
  • Production of medical radioisotopes
  • Particle accelerators and artificial elements
  • The work of Irène Joliot-Curie and Frédéric Joliot-Curie in artificial radioactivity

Explicit Instruction

Artificial transmutation is a nuclear process where humans cause a nucleus to change by bombarding it with particles.

The target nucleus absorbs or interacts with the incoming particle. The nucleus may then become unstable and emit another particle, forming a new nuclide.

A simple way to describe artificial transmutation is:

Target nucleus + incoming particle new nucleus + emitted particle

This differs from natural radioactive decay:

Natural radioactive decayArtificial transmutation
Occurs spontaneouslyCaused deliberately
Unstable nucleus decays by itselfNucleus is bombarded by a particle or nucleus
Often emits alpha, beta or gamma radiationMay absorb or emit neutrons, protons, alpha particles or gamma radiation
Example: uranium decayExample: neutron capture in a reactor

Example of natural decay:

Example of artificial transmutation:

In the artificial transmutation example, cobalt-59 absorbs a neutron to form cobalt-60. Cobalt-60 is radioactive and is used in medical and industrial applications.

Worked Examples

Worked Example 1

Describe why the following reaction is artificial transmutation:

Step 1: Identify the target nucleus.

The target nucleus is nitrogen-14:

Step 2: Identify the bombarding particle.

The incoming particle is an alpha particle:

Step 3: Identify the product nucleus.

The product nucleus is oxygen-17:

Step 4: Describe the change.

Nitrogen has atomic number . Oxygen has atomic number .

Since the atomic number has changed, the element has changed.

Step 5: State why it is artificial.

The reaction was caused by bombardment with an alpha particle, so it is artificial transmutation.

Final answer:

This is artificial transmutation because a nitrogen nucleus is deliberately bombarded with an alpha particle and changed into an oxygen nucleus.

Worked Example 2

Complete the following artificial transmutation equation:

Step 1: Balance mass number .

Left side:

Misplaced & A_{\text{left}}&=27+4\\ &=31 \end{align}

Right side:

Misplaced & A_{\text{right}}&=30+A\\ 31&=30+A\\ A&=1 \end{align}

Step 2: Balance atomic number .

Left side:

Right side:

Step 3: Identify the missing particle.

A particle with and is a neutron:

Final equation:

Final answer:

The missing particle is a neutron, .

Worked Example 3

Cobalt-59 is bombarded with a neutron to form cobalt-60 and gamma radiation.

Write the balanced nuclear equation and describe the reaction.

Step 1: Write the target nucleus.

Step 2: Write the incoming particle.

Step 3: Write the product nucleus.

When the nucleus absorbs a neutron, its mass number increases by , while atomic number remains the same.

Step 4: Include gamma radiation.

Step 5: Write the equation.

Step 6: Check conservation.

Mass number:

Atomic number:

Final answer:

This is artificial transmutation because cobalt-59 is changed into cobalt-60 by neutron bombardment.

Check for Understanding

Check 1

Question:

Is the following reaction natural radioactive decay or artificial transmutation?

Answer:

This is natural radioactive decay because the uranium nucleus decays spontaneously and is not bombarded by an incoming particle.

Check 2

Question:

Is the following reaction artificial transmutation?

Answer:

Yes. A boron nucleus is bombarded by a neutron and changed into lithium, so it is artificial transmutation.

Check 3

Question:

Complete the missing particle:

Solution:

Mass number:

Atomic number:

The missing particle is:

Final equation:

Investigation (Alternative to Explicit)

Hypothesis

If a nucleus is bombarded with a particle, then the products of the nuclear reaction can be predicted by conserving mass number and atomic number .

Data Collection

Students are given a set of artificial transmutation equations with missing particles or nuclides.

Example data table:

ReactionMissing particle or nuclide

Students calculate the missing mass number and atomic number for each unknown.

Analysis

Students compare the total mass number and atomic number on each side of the reaction.

For each reaction:

Students identify whether the product nucleus is a different element from the target nucleus.

If the atomic number changes, the element has changed.

Evaluation

Students evaluate whether their completed equations satisfy conservation of mass number and atomic number.

Students should discuss:

  • whether the equation is balanced
  • whether the reaction is natural or artificial
  • whether the target nuclide has changed into a different element
  • whether the reaction could produce useful radioisotopes

Problems

The following problems are designed to practise describing artificial transmutation and balancing nuclear equations.

  1. Define artificial transmutation in one sentence.

  2. Explain why artificial transmutation is a nuclear reaction rather than a chemical reaction.

  3. Identify the target nucleus, incoming particle and product nucleus in the following reaction:

  4. Complete the equation:

  5. Complete the equation:

  6. Complete the equation:

  7. Explain why the following reaction is not artificial transmutation:

  8. A nucleus absorbs a neutron. Describe what happens to its mass number and atomic number.

  9. A nucleus absorbs a proton. Describe what may happen to its atomic number.

  10. Compare artificial transmutation and natural radioactive decay using two similarities and two differences.

Followup

Self-check

Students should be able to answer the following questions:

  • Can I define artificial transmutation?
  • Can I identify the target nucleus and bombarding particle in a nuclear equation?
  • Can I balance a nuclear equation using mass number and atomic number?
  • Can I explain how artificial transmutation can change one element into another?
  • Can I distinguish artificial transmutation from natural radioactive decay?

Next Topic

The next topic is nuclear fission and nuclear fusion.

Students will use their understanding of artificial transmutation to describe how nuclear reactions can produce new nuclei and release energy.

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