• Quick retrieval from earlier learning (Protons, neutrons and electrons). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Which particle is in the nucleus with no charge? (proton / neutron / electron) → neutronPrompt: Two of the particles are in the nucleus.
2. Atomic structure: which statement is true? (The plum pudding model is today's accepted model of the atom. / Neutrons have a negative charge. / Protons and electrons have the same mass. / Atoms are mostly empty space.) → Atoms are mostly empty space.Prompt: Where is each particle, and what is its charge?
3. Which particle is found in shells around the nucleus? (proton / neutron / electron) → electronPrompt: Two of the particles are in the nucleus.

• Show the periodic table and ask what patterns students can see before anything is explained.
• Share the objective: How the model of the atom changed over time. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Which particle did James Chadwick discover in 1932?
• Step 1: Chadwick showed the nucleus contains uncharged neutrons as well as protons.
• Step 2: So the answer is: the neutron
• Answer: the neutron
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. In Rutherford's experiment, most alpha particles went straight through thin gold foil. What did this show? (Atoms are solid spheres / Gold has no electrons / Alpha particles are negative / Most of the atom is empty space) → Most of the atom is empty spacePrompt: If atoms were solid, what would the particles do?
2. Models of the atom: which statement is NOT true? (In the plum pudding model, electrons orbit a nucleus. / The nucleus is tiny compared with the whole atom. / The electron was discovered before the nucleus. / Bohr's model put electrons in shells at fixed distances.) → In the plum pudding model, electrons orbit a nucleus.Prompt: Did the plum pudding model have a nucleus?

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 5 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. Models of the atom: which statement is NOT true? (The nucleus is tiny compared with the whole atom. / The electron was discovered before the nucleus. / Scientific models change when new evidence is found. / Rutherford discovered the neutron.) → Rutherford discovered the neutron.Prompt: Did the plum pudding model have a nucleus?
2. A very few alpha particles bounced back from the gold foil. What did this show? (Electrons are heavy / Atoms are spread evenly with positive charge / The foil had holes / There is a tiny, dense, positively charged nucleus) → There is a tiny, dense, positively charged nucleusPrompt: Alpha particles are positive. What would repel them strongly?

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-8.