Year 8 Science · Unit 2 · Lesson 06
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Learning Goals
Match each part to its description
Write the matching letter in the middle column. Each letter is used once.
| Part | Letter | Description |
|---|---|---|
| Proton | A. A whole atom whose charges balance, because it has as many electrons as protons. | |
| Neutron | B. The tiny, dense centre of an atom that holds almost all of its mass. | |
| Electron | C. A particle in the nucleus that carries no charge. | |
| Nucleus | D. A particle in the nucleus that carries a positive charge (+1). | |
| Neutral atom | E. A very light particle outside the nucleus that carries a negative charge (−1). |
1. The carbon atom in the lesson has six of each kind of subatomic particle. Work out how many particles are packed into its nucleus and how many move around outside it, and name them.
Name the particle from the clue
For each clue, write every particle it could be. Then write Yes if the clue alone is enough to name one particle, or No if it is not.
| Clue about a mystery particle | Could be | Enough on its own? (Yes or No) |
|---|---|---|
| It is found in the nucleus. | ||
| Its charge is −1. | ||
| It is much heavier than an electron. | ||
| It has no charge. |
Cause and effect
Scenario: pressing on a table
An atom is almost entirely empty space, with a tiny nucleus at its centre and electrons moving far out around it. Yet when you press on a table, your hand stops at the surface.
Complete the chain to explain why your hand cannot pass straight through. Each box follows from the box before it.
Where is the mass?
Scientists compare particle masses using relative mass, where a proton counts as 1. Use the table to find how the mass of a carbon atom is shared out.
| Particle | Relative mass | Number in one carbon atom | Total relative mass |
|---|---|---|---|
| Proton | 1 | 6 | |
| Neutron | 1 | 6 | |
| Electron | 0.0005 | 6 |
Data: relative masses rounded. A neutron is very slightly heavier than a proton, and an electron is about 1/1836 of a proton.
2. Complete the last column of Table 1. Then calculate the total relative mass of the nucleus, and how many times heavier the nucleus is than all six electrons together.
Answer times heavier
3. The lesson says an atom’s mass is set by its nucleus, but its size is set by how far out its electrons reach. Use your answer to Question 2 to explain both halves of this statement.
4. Textbooks draw an atom as a small cluster of balls with a few dots around it. Explain why this simple atom model is useful even though it is not realistic. Describe what it shows correctly, and two things it gets wrong about a real atom.
Match each part to its description
Proton → D; Neutron → C; Electron → E; Nucleus → B; Neutral atom → A.
1. 12 in the nucleus (6 protons and 6 neutrons); 6 outside it (the 6 electrons). [2 marks]
Name the particle from the clue
In the nucleus: proton or neutron; No. Charge −1: electron; Yes. Much heavier than an electron: proton or neutron; No. No charge: neutron; Yes. Point to draw out: charge alone names every particle, location and mass do not.
Cause and effect
Box 2: the outsides of the atoms in your hand and in the table are electrons, which carry a negative charge. Box 3: negative charges repel each other, so the electrons of the two surfaces push against each other (electrostatic repulsion).
Go Deeper
2. Totals: protons 6; neutrons 6; electrons 6 × 0.0005 = 0.003. Nucleus = 6 + 6 = 12. 12 ÷ 0.003 = 4000 times heavier (about 3700 times with unrounded values; accept either). [3 marks: 1 column, 1 nucleus 12, 1 about 4000]
3. Mass: the nucleus is about 4000 times heavier than all the electrons, so almost all the mass (more than 99.9%) is in the nucleus. Size: the nucleus is tiny and sits at the centre, while the electrons move in the space far out around it, so the edge of the atom is set by where the electrons are. [3 marks: 1 mass with data, 1 nucleus tiny, 1 electrons set the size]
Show What You Know
4. Marking guide (points expected): 1 shows the three particles; 1 shows their charges (+, 0, −) and that protons and neutrons are in the nucleus with electrons outside; 1 limit: not to scale, the real atom is about 100 000 times wider than its nucleus and is almost entirely empty space; 1 a second limit: electrons are drawn as fixed dots, but they move in the space around the nucleus (or: electrons are drawn too big for their tiny mass); 1 evidence: the nucleus holds nearly all the mass (Q2), which a drawing with similar-sized balls and dots does not make clear; 1 judgement: useful because it clearly communicates the parts and their positions, which is what we need to reason about. [6 marks]
Common error to watch for: in the clue table, writing “proton” for “found in the nucleus”. Location narrows three particles to two; only charge settles it.