Students describe the nuclear atom (protons and neutrons in the nucleus, electrons in shells), use atomic and mass numbers to count each particle, and connect the model to the evidence that replaced earlier ones (AC9S9U06, node 1, 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 7 min · Explain 12 min · Evaluate 3 min · Typical adds 4 min, Wider about 4 min
A concept tutorial for introducing or revising the idea; it does not replace a timeline of atomic models or a gold-foil analogy activity. Set the width with ?width=minimum, typical (default) or wider.
The hinge: students arrive with Year 7 particles that have no inside, so the model has to be extended explicitly. The prediction asks for neutrons from the two numbers before students meet the rule; the usual slips are taking the mass number as the neutrons, or adding the numbers.
Board notes: the Bohr model is drawn not to scale (the nucleus would be about 100 000 times smaller than the atom). Shells fill 2, 8, 8, 2; this lesson doesn't need shells beyond "electrons around the nucleus" (Year 10 Shells does). Protons up to 20, neutrons up to 24.
Using atomic and mass numbers to count protons, neutrons and electrons. When a student says carbon-12 has 12 neutrons, ask what the mass number counts.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student says carbon-12 has 12 neutrons. | What does the mass number count? | Protons plus neutrons. Subtract the protons (the atomic number): 12 − 6 = 6. |
| A student changes the protons to make a heavier carbon. | What happened to the element's name on the board? | Protons decide the element. Add neutrons for a heavier atom of the same element. |
| A student thinks electrons hold most of the mass because they fill the atom. | What is the mass of an electron compared with a proton? | About 1/1840: almost nothing. The nucleus is tiny but holds nearly all the mass. |
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: Carbon-14 is used to date old wood and bone. How is a carbon-14 atom different from carbon-12, and how is it the same?
Support: Give the frame: 'Atomic number = protons = … . Mass number − atomic number = neutrons = … . Neutral, so electrons = … .'
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's inside an atom?". The idea: The nuclear model of the atom — protons, neutrons and electrons: I can describe the structure of the nuclear atom in terms of protons, neutrons and electrons, and use atomic number and mass number to describe specific atoms. What understanding looks like: - Describes the nuclear atom: protons and neutrons in the nucleus, electrons in shells - Uses atomic number and mass number to determine proton, neutron and electron counts - Describes the relative mass and charge of protons, neutrons and electrons Mistakes students often make here: - A student says carbon-12 has 12 neutrons. - A student changes the protons to make a heavier carbon. - A student thinks electrons hold most of the mass because they fill the atom. 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. - 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's inside an atom?".
Oxygen has atomic number 8 and mass number 16. How many protons, neutrons and electrons does a neutral oxygen atom have?
8 protons, 8 neutrons (16 − 8), 8 electrons.
Next: isotopes (node 2), then alpha, beta and gamma decay (node 3), half-life (node 4); decay chains are a class task (node 5). In Year 10, Shells uses the same board to arrange electrons.
In class: a timeline of atomic models (Dalton, Thomson, Rutherford, Bohr) with the evidence for each change; a "mystery box" gold-foil analogy (rolling marbles at a hidden shape).