The shape of the lesson
By the end of the lesson, learners can
- Look inside the atom: Explore the nucleus and the orbiting electrons, and see how little of the atom is actually filled.
- Tiny core, huge space: The nucleus is thousands of times smaller than the atom but holds almost all the mass.
- Nucleus: small, central, positive, holds almost all the mass.
- Electrons: negative, orbit the nucleus, very light.
- Size: the nucleus is tiny, so the atom is mostly empty space.
One picture every idea returns to
An atom is mostly empty space, with a tiny, dense, positively charged nucleus of protons and neutrons at the centre and electrons orbiting around it. Almost all the mass of the atom is in the nucleus.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, A speck of mass in empty space.. If an atom were the size of a stadium, its nucleus would be a pea on the centre spot. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Look inside the atom | Explore the nucleus and the orbiting electrons, and see how little of the atom is actually filled. Project tab 1 of the lab (Atomic structure) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Tiny core, huge space | The nucleus is thousands of times smaller than the atom but holds almost all the mass. | Jigsaw |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 13 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Tiny core, huge space, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Jigsaw
Split the content into expert pieces. Expert groups master one piece each, then regroup so every home team has one expert per piece, and each expert teaches their piece to the team.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Nearly all the mass of an atom is in the nucleus, even though the nucleus is thousands of times smaller than the atom. | The electrons fill the volume but contribute almost no mass. |
Atomic structure: worksheet
6 questions, 13 marks. Written in the style of the papers; no past paper question is reproduced.
Describe the structure of an atom. State what is at the centre and what is found around it.
State the charge on the nucleus and the charge on an electron.
Almost all of the mass of an atom is found in one place. State where, and name the much lighter particles found in the rest of the atom.
A student says that an atom is solid all the way through. Explain why this is wrong.
Explain what keeps the negative electrons moving around the nucleus instead of flying away.
A complete atom has no overall charge. Explain why, in terms of the positive and negative charges it contains.
Answer key and marking notes
- There is a small nucleus at the centre. ✓
- The nucleus is positively charged. ✓
- Negatively charged electrons move around the nucleus in orbits. ✓
- The nucleus is positively charged. ✓
- An electron is negatively charged. ✓
- Almost all the mass is in the nucleus. ✓
- The much lighter particles are the electrons. ✓
- The nucleus is extremely small compared with the whole atom. ✓
- The electrons orbit far out, so most of the atom is empty space. ✓
- There is an electrostatic attraction between the negative electrons and the positive nucleus. ✓
- This pull holds the electrons in their orbits. ✓
- An atom has equal numbers of positive charges (in the nucleus) and negative electrons. ✓
- The equal positive and negative charges cancel, so the atom is neutral overall. ✓
2 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
What is found at the centre of an atom, and what moves around it?
- AA nucleus of protons and neutrons sits at the centre, with electrons orbiting it.
- BElectrons sit at the centre, with protons orbiting them.
- CThe atom is a solid ball of protons throughout.
- DNeutrons orbit a nucleus made of electrons.
Where is nearly all of the mass of an atom concentrated?
- Ain the nucleus
- Bin the orbiting electrons
- Cspread evenly through the whole atom
- Din the empty space between the electrons
Quiz key
Protons and neutrons form a tiny central nucleus, while the much lighter electrons orbit it. The electrons are not at the centre, and the atom is mostly empty space rather than solid.
Almost all the mass is in the nucleus, because protons and neutrons are about 1800 times heavier than electrons. The electrons contribute very little to the total mass.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.