AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Before the discovery of the electron, atoms were thought to be tiny…
Full specification wording
The development of the model of the atom (common content with chemistry): Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.
The earliest scientific model of the atom, set out by John Dalton at the beginning of the nineteenth century, treated each atom as a tiny solid sphere with no internal structure and no parts.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 2 of 12
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The earliest scientific model of the atom, set out by John Dalton at the beginning of the nineteenth century, treated each atom as a tiny solid sphere with no internal structure and no parts. It was a useful model because it explained how elements combine in fixed ratios to form compounds, and why mass is conserved in a reaction. What it said nothing about was electric charge, because at that time no smaller particle was known. Once Thomson identified the electron, a particle far lighter than any atom and carrying a negative charge, the idea that an atom could not be divided had to be abandoned, and the modelling of what is inside the atom began.
What earns the marks
- The atom being described as a tiny solid sphere.
- Stating that it was thought it could not be divided, having no internal structure.
- Placing this model before the discovery of the electron.
- Stating that the discovery of the electron showed the atom could be divided after all.
Common mistakes and how to put them right
Including a nucleus in the earliest model of the atom.
Saying the sphere model already contained electrons.
Placing this model after the plum pudding model in the sequence.
Crediting Rutherford with the indivisible sphere idea.
Exam tips
- Learn the sequence as a list: solid sphere, plum pudding, nuclear, Bohr, then the neutron.
- Say what each model could not explain; that is usually what the next mark is for.
- Keep the word indivisible or could not be divided in the answer, because it is the defining feature.
Try the lesson
The start of the The development of the model of the atom (common content with chemistry): Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided. lesson, made from checked teaching notes for this specification point.
Have a go first
Before the discovery of the electron, how did scientists describe the structure of atoms?
Listen
The earliest scientific model of the atom, set out by John Dalton at the beginning of the nineteenth century, treated each atom as a tiny solid sphere with no internal structure and no parts. It was a useful model because it explained how elements combine in fixed ratios to form compounds, and why mass is conserved in a reaction. What it said nothing about was electric charge, because at that time no smaller particle was known. Once Thomson identified the electron, a particle far lighter than any atom and carrying a negative charge, the idea that an atom could not be divided had to be abandoned, and the modelling of what is inside the atom began. A strong answer earns marks for these points. the atom being described as a tiny solid sphere. stating that it was thought it could not be divided, having no internal structure. placing this model before the discovery of the electron. stating that the discovery of the electron showed the atom could be divided after all. Exam tip: Learn the sequence as a list: solid sphere, plum pudding, nuclear, Bohr, then the neutron.
See it
Put it in order
Put these steps in the order they happen.
- 1. No internal structure
- 2. Could not be divided
- 3. Atoms thought to be tiny spheres
- 4. Modelling of what is inside the atom began
- 5. Atom could be divided after all
- 6. Electron discovered
Key words
Say what each word means before you turn the card.
solid sphere model
Try answering aloud or in your head before turning the card.
indivisible atoms
Try answering aloud or in your head before turning the card.
discovery of the electron
Try answering aloud or in your head before turning the card.
See every definition
- solid sphere model
- The earliest scientific model of the atom, set out by John Dalton, treated each atom as a tiny solid sphere with no internal structure and no parts.
- indivisible atoms
- Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.
- discovery of the electron
- Thomson identified a particle far lighter than any atom and carrying a negative charge, so the idea that an atom could not be divided had to be abandoned.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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