Students arrange the electrons of elements 1 to 20 in shells (2, 8, 8, 2) and identify the outer-shell electrons, the variable the periodic table depends on (AC9S10U06, 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 10 min · Evaluate 3 min · Typical adds 4 min, Wider about 2 min
A concept tutorial for introducing or revising the idea; it builds on Year 9's nuclear atom (What's inside an atom?). Set the width with ?width=minimum, typical (default) or wider.
The hinge is fluency: students who can't place outer electrons quickly can't use the periodic table later. The Explain checks and the book task are practice, not breadth.
Board notes: the Bohr model, not to scale. Shells hold 2, 8, 8, then 2 (the simple rule for elements 1 to 20; the third shell holds more in heavier atoms, which Year 10 doesn't need).
Filling shells in order, 2 then 8 then 8. When a student writes 2, 8, 9, ask how many the third shell holds for the first 20 elements.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student writes 2, 8, 9 for potassium. | How many does the third shell hold for elements 1 to 20? | 8. The 19th electron starts a fourth shell: 2, 8, 8, 1. |
| A student counts protons into the shells. | Which particles are in the shells, and which in the nucleus? | Only electrons are in shells; in a neutral atom there are as many as there are protons. |
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.
Stretch: Why does the periodic table have 2 elements in its first row and 8 in the next two?
Support: Give a shell template (three circles with 2, 8, 8 boxes) to fill in for each element.
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 10 student in Australia. Help me understand ONE idea only, from the lesson "How are the electrons arranged?". The idea: Electron shell configuration and the Bohr model: I can draw or describe the electron shell configuration of elements 1–20 using the Bohr model and explain the shell-filling rules. What understanding looks like: - Draws a correct Bohr diagram for any element 1–20 - States the maximum electron capacity of the first three shells (2, 8, 8) - Identifies the number of outer-shell electrons for any element 1–20 Mistakes students often make here: - A student writes 2, 8, 9 for potassium. - A student counts protons into the shells. 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 "How are the electrons arranged?".
Write the electron arrangement of aluminium (13 electrons). How many outer electrons does it have?
2, 8, 3: three outer electrons.
Next: Why do elements in a group behave alike? (node 2), then periodic trends (node 3); predicting properties from position is a class task (node 4).
In class: flame tests (sodium, potassium, lithium, copper chlorides) with a hand spectroscope if available.