AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Niels Bohr adapted the nuclear model by suggesting that electrons orbit…
Full specification wording
The development of the model of the atom (common content with chemistry): Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances.
Rutherford's nuclear model left a problem: electrons circling a positive nucleus should lose energy continuously and spiral into it, so atoms should collapse.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 7 of 12
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Rutherford's nuclear model left a problem: electrons circling a positive nucleus should lose energy continuously and spiral into it, so atoms should collapse. Bohr adapted the model rather than replacing it. He kept the nucleus and the orbiting electrons, but proposed that the electrons can only occupy certain fixed distances from the nucleus, not any distance at all. Each allowed distance corresponds to a definite energy, which is where the energy levels used in electron arrangements come from. An electron can move between levels by absorbing or emitting electromagnetic radiation, but it cannot sit anywhere in between, so the atom is stable.
What earns the marks
- Stating that electrons orbit the nucleus at specific fixed distances.
- Stating that Bohr adapted the nuclear model rather than replacing it.
- Stating that electrons cannot occupy any distance from the nucleus, only certain allowed ones.
- Linking the fixed distances to the energy levels used in electron arrangements.
Common mistakes and how to put them right
Saying Bohr replaced or overturned the nuclear model.
Crediting Bohr with the discovery of the nucleus.
Describing Bohr's electrons as spread through a cloud at any distance.
Attributing the discovery of the proton or neutron to Bohr.
Exam tips
- Use the word adapted; it is the specification's own wording and marks the difference from a replacement.
- Say specific or fixed distances, not just orbits, because any orbit was already in the nuclear model.
- Connect Bohr's levels to the 2,8,8 electron arrangements you already use.
Try the lesson
The start of the The development of the model of the atom (common content with chemistry): Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. lesson, made from checked teaching notes for this specification point.
Have a go first
In Bohr's adaptation of the nuclear model, where are the electrons found?
Listen
Rutherford's nuclear model left a problem: electrons circling a positive nucleus should lose energy continuously and spiral into it, so atoms should collapse. Bohr adapted the model rather than replacing it. He kept the nucleus and the orbiting electrons, but proposed that the electrons can only occupy certain fixed distances from the nucleus, not any distance at all. Each allowed distance corresponds to a definite energy, which is where the energy levels used in electron arrangements come from. An electron can move between levels by absorbing or emitting electromagnetic radiation, but it cannot sit anywhere in between, so the atom is stable. A strong answer earns marks for these points. stating that electrons orbit the nucleus at specific fixed distances. stating that Bohr adapted the nuclear model rather than replacing it. stating that electrons cannot occupy any distance from the nucleus, only certain allowed ones. linking the fixed distances to the energy levels used in electron arrangements. Exam tip: Use the word adapted; it is the specification's own wording and marks the difference from a replacement.
See it
Put it in order
Put these steps in the order they happen.
- 1. Electrons orbit the nucleus at specific fixed distances
- 2. Bohr adapted the model rather than replacing it
- 3. Nuclear model: electrons orbit the nucleus
- 4. Energy levels used in electron arrangements
- 5. Each allowed distance corresponds to a definite energy
- 6. Electrons cannot occupy any distance from the nucleus, only certain allowed ones
Key words
Say what each word means before you turn the card.
Bohr model
Try answering aloud or in your head before turning the card.
fixed orbits
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energy levels
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See every definition
- Bohr model
- A development of the nuclear model in which electrons orbit the nucleus at specific distances.
- fixed orbits
- The certain fixed distances from the nucleus that electrons can only occupy, rather than any distance at all.
- energy levels
- Each allowed distance corresponds to a definite energy, and these are used in electron arrangements.
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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