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Chemistry

Workhorse studio concept for the American Association of Chemistry Teachers. This app has not been commissioned or approved by AACT.

MapUnit 9, Nuclear chemistry

9.1Radioactive decay

Why some nuclei are unstable, what alpha, beta and gamma decay change, and what stops each.

Explore radioactive decay

Inspect a nuclear change, compare carbon isotopes, or test a barrier.

Parent nucleusRa-226

Protons88

Neutrons138

Parent nucleus
Inspect radium-226 before the emission.

Drag to inspect a stage. Playback shows the sequence, not elapsed physical time.

→+

Alpha particles consist of two neutrons and two protons, just like a helium nucleus, so they are sometimes shown as helium-4.

One illustrative nuclear event. Scrubbing controls the drawing; it does not predict when a particular nucleus decays. Particle sizes and travel distances are enlarged for inspection.

Experiment results

Complete a run to keep its result here. Change the setup to compare another run.

About this model

The carbon bench looks up isotope stability and half-life. The shielding bench uses a simplified table of radiation and materials. The nuclear view follows one emission and balances its mass and atomic numbers. These views do not calculate a population decaying over time or the amount of radiation transmitted through a shield.

For alpha and beta radiation, “stops” marks the selected barrier in the teaching model. Actual gamma shielding reduces intensity by an amount that depends on the material, its thickness and the radiation energy.

Reference: OpenStax, Radioactive Decay

Reference: NRC, Minimize Your Exposure

Guided investigations and notebook

Investigation 1 of 2

Which carbon nuclei hold together?

Every carbon atom has six protons. Change the number of neutrons and see which nuclei are stable.

  1. Predict

    Carbon-12, with 6 neutrons, is stable. What happens with more neutrons?

    Make a guess before you run it. Being wrong here is useful.

  2. Run it

    Stable. About 99% of the carbon on Earth.

    Proton
    Positive charge
    Neutron
    No charge
    Carbon-12Stable

    What the bench showed

    Nothing yet. Each run adds a line here.

  3. Say what you found

  4. Check

    2 questions about what the bench shows open once your finding is in the notebook.

Investigation 2 of 2

What stops each kind of radiation?

Aim alpha, beta and gamma radiation at sheets of paper, aluminum and lead, and compare their penetration.

  1. Predict

    Which material is used here to attenuate gamma rays?

    Make a guess before you run it. Being wrong here is useful.

  2. Run it

    Shielding

    Radiation
    Material

    Choose radiation and materials, then run the experiment.

    Alpha: αBeta: βGamma: γPaperAluminum (not in place)Lead (not in place)

    Drag to inspect a stage. Playback shows the sequence, not elapsed physical time.

    Gamma shielding reduces intensity. The lead endpoint here marks attenuation, not complete absorption; thickness and radiation energy are not modeled.

    Your results 0 of 9 tested
    RadiationPaperAluminumLead
    Alpha: Not testedNot testedNot tested
    Beta: Not testedNot testedNot tested
    Gamma: Not testedNot testedNot tested
    About this model

    The carbon bench looks up isotope stability and half-life. The shielding bench uses a simplified table of radiation and materials. The nuclear view follows one emission and balances its mass and atomic numbers. These views do not calculate a population decaying over time or the amount of radiation transmitted through a shield.

    For alpha and beta radiation, “stops” marks the selected barrier in the teaching model. Actual gamma shielding reduces intensity by an amount that depends on the material, its thickness and the radiation energy.

    Reference: OpenStax, Radioactive Decay

    Reference: NRC, Minimize Your Exposure

    What the bench showed

    Nothing yet. Each run adds a line here.

  3. Say what you found

  4. Check

    2 questions about what the bench shows open once your finding is in the notebook.

What this topic builds

  • Name the decay from its equationNot practiced yet.
    Not started
  • Complete the products of a decayNot practiced yet.
    Not started
  • Find the parent nucleusNot practiced yet.
    Not started
  • Say why some nuclei are unstableNot practiced yet.
    Not started
  • Say what each decay changes in the nucleusNot practiced yet.
    Not started
  • Say what stops each kind of radiationNot practiced yet.
    Not started