Students define isotopes as atoms of the same element with different numbers of neutrons, explain why isotopes react alike, and recognise that some isotopes are unstable (AC9S9U06, node 2).
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 7 min · Explain 11 min · Evaluate 3 min · Typical adds 4 min, Wider about 4 min
A concept tutorial for introducing or revising the idea. Set the width with ?width=minimum, typical (default) or wider. It builds on What's inside an atom? (node 1), so set that first.
Not a hinge node, but its idea carries the next two: decay (only unstable isotopes decay) and half-life (carbon-14 dating). The prediction separates "more neutrons" from the usual slips: more protons, more electrons, or a different element.
Board notes: for elements 1 to 20 the board says whether the nucleus you built is stable or radioactive (from the list of stable isotopes; very long-lived calcium-48 counts as stable). It does not say how an unstable nucleus decays: that is the next lesson's board. Nuclei far from the stable ones are listed as radioactive even though some would not hold together at all.
Separating 'same element' from 'same atom'. Ask which number on the board stayed the same and which changed, before giving the word isotope.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student adds protons to make carbon-14. | What happened to the name at the top of the board? | It changed to nitrogen, then oxygen. Protons decide the element; change the neutrons for a heavier carbon. |
| A student thinks carbon-14 reacts differently because it is heavier. | Which particles take part in reactions? | The electrons. Both isotopes have 6, arranged the same way, so they react the same way. |
| A student thinks 'radioactive' means the whole atom is dangerous to touch or reacts strongly. | Which part of the atom is unstable? | Only the nucleus. It decays now and then, giving out radiation; chemically it is ordinary carbon. |
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.
Stretch: Hydrogen has three isotopes: hydrogen-1, -2 (deuterium) and -3 (tritium). Which is radioactive? Use the board to check. (Tritium, hydrogen-3.)
Support: Give the frame: 'Carbon-12 and carbon-14 both have … protons, so they are both … . Carbon-14 has … more neutrons, so its mass number is … .'
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 "Same element, different atoms?". The idea: Isotopes — same element, different neutron numbers: I can define isotopes as atoms of the same element with different numbers of neutrons, and explain why some isotopes are unstable. What understanding looks like: - Defines isotopes as atoms of the same element with different numbers of neutrons - Identifies that some isotopes are unstable and undergo radioactive decay - Uses isotope notation (e.g. carbon-14) correctly Mistakes students often make here: - A student adds protons to make carbon-14. - A student thinks carbon-14 reacts differently because it is heavier. - A student thinks 'radioactive' means the whole atom is dangerous to touch or reacts strongly. 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 (The nuclear model of the atom — protons, neutrons and electrons), 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 "Same element, different atoms?".
Uranium-235 and uranium-238 both have 92 protons. How many neutrons does each have, and are they the same element?
143 and 146 neutrons. Both are uranium (92 protons): they are isotopes.
Next: alpha, beta and gamma (node 3), then half-life (node 4), which uses carbon-14 for dating.
In class: a "same and different" table for isotopes of hydrogen, carbon and chlorine; relative atomic mass from isotope abundances (the Wider step) if the class has met averages.