Students describe alpha, beta and gamma decay by what leaves the nucleus, explain how alpha and beta decay change the atomic and mass numbers, and compare how far each gets (AC9S9U06, node 3, a hinge node).
Load these into Waypoints Prepare: choose Load URL and paste the copied address, or download the file and import it. In Prepare, the worksheet's Teacher edition shows the answers; the student copy hides them.
Engage and Explore 8 min · Explain 12 min · Evaluate 3 min · Typical adds 5 min, Wider about 5 min
A concept tutorial for introducing or revising the idea; it does not replace a teacher demonstration with sealed sources and a Geiger counter (or a video of one). Set the width with ?width=minimum, typical (default) or wider.
The hinge: students often run the three kinds together (gamma "turns it into a new element"; beta electrons "come from the shells"), or cannot track the numbers. The prediction asks for the product of one alpha decay before students meet the rule; the usual slips are changing only the mass number, or moving the wrong way in the table.
Board notes: the decay board takes any isotope up to uranium (isotope: radon-222). It knows how about 25 common isotopes really decay (the uranium-238 and radon-222 chains, carbon-14, iodine-131, cobalt-60, caesium-137, americium-241 and others) and says so; for the rest it says it has no data. Students can still press any button: a "wrong" decay is a good discussion ("In nature C-14 decays by beta, not alpha"). The nucleus shows at most 60 particles, in the right proportion of protons to neutrons; it is not to scale. Beta here is beta-minus only (no positrons). The shield board is schematic: real ranges depend on energy.
Tracking two numbers at once. When a student guesses the product, ask them to write the protons and the mass number separately before and after, and wait.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student says gamma decay makes a new element. | What leaves in gamma: protons, neutrons or neither? | Neither: only energy. Same protons, same element, same mass number. |
| A student says the beta electron came from the electron shells. | Which number changes in beta decay? | The atomic number goes up by 1: a neutron in the nucleus became a proton, and the electron made with it shot out. The shells are not involved. |
| A student subtracts 2 from the mass number in alpha decay. | How many particles are in an alpha particle? | Four: 2 protons and 2 neutrons. Mass number down 4, atomic number down 2. |
| A student thinks alpha is the least dangerous in every situation. | What stops alpha, and is there any of that inside your lungs? | Alpha is stopped quickly because it hits atoms hard; inside the body it gives all that energy to nearby cells. Danger depends on where the source is. |
One possible solution for each task. Other correct programs are fine.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Stretch: Uranium-238 decays by alpha, then beta, then beta. Write each new nucleus. (Thorium-234, protactinium-234, uranium-234: after three decays it is uranium again, but lighter.)
Support: Give the table to fill in: 'Alpha: leaves … · atomic number … · mass number … · stopped by …', and the same for beta and gamma.
For a student who has done the lesson and is still stuck. They paste it into an AI tool your school allows; it asks questions about this lesson's one idea and doesn't give answers. Students see it on the course recap page only through a link ending in ?coach=1: recap with coach prompts.
You are a patient science coach for a Year 9 student in Australia. Help me understand ONE idea only, from the lesson "What comes out of a decaying nucleus?". The idea: Types of radioactive decay — alpha, beta and gamma: I can describe alpha, beta and gamma decay in terms of what is emitted and how each changes the nucleus, and compare their penetrating power. What understanding looks like: - Describes what is emitted in alpha, beta and gamma decay - Explains how alpha and beta decay change the atomic number and mass number of the nucleus - Compares the penetrating power of alpha, beta and gamma radiation Mistakes students often make here: - A student says gamma decay makes a new element. - A student says the beta electron came from the electron shells. - A student subtracts 2 from the mass number in alpha decay. How to coach me (rules from the Waypoints Kit coach): - Ask me one short question at a time (2 to 4 sentences) and wait for my answer. Never give me the answer before you have heard my thinking, and don't hide the answer inside your question. - Start in Discover: ask me to explain the idea in my own words, or to predict what happens in a simple example. I can switch any time: "teach it back" (you play a beginner and I explain), "spot the flaw" (you show me an answer with one common mistake and I find it), or "check" (I explain, and you tell me what is solid and what to revisit). - If I am stuck or say "just tell me", ask what I think first, then give a small hint or a simpler example. Explain only after I have had a real go. - If I seem to be missing the idea that comes before this one (Isotopes — same element, different neutron numbers), check it quickly, then come back. - Stay in this idea: don't teach later ideas or add extra content. If I ask about something else, say it is for another lesson and bring me back. - After you help, ask me one reflective question, such as how I know my answer is right or what I would check. - Praise my effort and method, not my ability. - You can be wrong: if I rely on something you said, remind me to check it against my notes or the lesson. If you don't know, say so. - Use simple words. - Stop when I can explain the idea in my own words and get one new example right. Then tell me to go back to the lesson "What comes out of a decaying nucleus?".
Cobalt-60 (27 protons) decays by beta decay and gives out gamma rays. What is it now, and which of the radiation would get through 1 cm of aluminium?
Nickel-60 (28 protons, mass number still 60). Only the gamma rays get through the aluminium.
Next: How long does radioactivity last? (half-life, node 4). Node 5, decay chains, is a class task: the decay board with isotope: uranium-238 lets students follow the real chain to lead-206 (the board says when each step is the real one and when it reaches a stable isotope).
In class: a teacher demonstration or video of sealed sources, absorbers and a Geiger counter; a card sort of uses (smoke alarm, thyroid treatment, medical imaging, thickness gauges for paper and foil, checking welds in aircraft).