Explain why electrons in an atom can be found at different distances from the nucleus, and describe what happens to an electron when it absorbs energy.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Electrons occupy shells (energy levels) around the nucleus.
Different shells are at different distances from the nucleus – each shell is at a fixed, larger radius than the one below it.
When an electron absorbs energy it jumps to a higher energy level, i.e. to a shell further from the nucleus.
The electron then returns to a lower energy level (often its original shell), releasing the absorbed energy.
The released energy is emitted as electromagnetic radiation – light.
Different shells are at different distances from the nucleus – each shell is at a fixed, larger radius than the one below it.
When an electron absorbs energy it jumps to a higher energy level, i.e. to a shell further from the nucleus.
The electron then returns to a lower energy level (often its original shell), releasing the absorbed energy.
The released energy is emitted as electromagnetic radiation – light.
Examiner tips
- Use the term "shells" or "energy levels". Mention that higher shells are further from the nucleus. Explain the absorption–emission cycle. Include that the released energy appears as light.
Common mistakes
- Saying electrons are in the nucleus. Forgetting that higher shells are further from the nucleus. Not stating that the released energy is light (electromagnetic radiation).
Mark scheme (5 marks)
- Electrons occupy shells (energy levels) around the nucleus
- Different shells are at different distances from the nucleus / shells are at fixed distances from the nucleus
- When an electron absorbs energy it moves to a higher energy level / shell further from the nucleus
- The electron then returns to a lower energy level / its original shell, releasing energy
- The energy released is emitted as electromagnetic radiation / light
Related
- All AQA A-Level Chemistry (7405) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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