3.2.1Interactions with the Environment
Absorption and Emission Of Radiation
5 min read 6 parts Lesson 10 of 27 Unit quiz
Section 1 of 6Electrons and energy levels
Arrangement
- Arrangement Electrons in an atom occupy energy levels (shells) at different distances from the nucleus.
- Lower levels are closer to the nucleus; higher levels are further away and hold electrons with more energy.
Fixed jumps
- Fixed jumps An electron can only move between levels by gaining or losing the exact energy difference between them.
Scope of the topic
- Scope of the topic You only need the idea of levels and jumps here;
- how many electrons fill each shell belongs to chemistry.
Section 2 of 6From absorption to emission
1Radiation arrives
- Radiation arrives Electromagnetic waves such as light or heat reach the atom.
2Electron absorbs it
- Electron absorbs it The electron takes in the energy and moves up to a higher energy level.
3Unstable state
- Unstable state An electron in a raised level is unstable and will not stay there.
4Electron falls back
- Electron falls back It drops to a lower level and gives out the extra energy as a wave of electromagnetic radiation.
Section 3 of 6Size of the jump and the radiation
| Energy jump | Radiation emitted | Example |
|---|---|---|
| Larger drop between levels | Higher frequency (more energy per wave) | Mercury atoms give out ultraviolet |
| Smaller drop between levels | Lower frequency | Neon and sodium atoms give out visible light |
| Many different drops possible | A set of separate frequencies | A coloured line pattern unique to the element |
Section 4 of 6Why this matters
Energy level changes
Colours of light
- Colours of light The colours seen in a visible spectrum come from electrons moving down between levels.
Fingerprint of an element
- Fingerprint of an element Each element has its own pattern of levels, so it emits its own characteristic frequencies.
Light sources
- Light sources Neon signs and sodium street lamps glow because their atoms emit visible radiation in this way.
Section 5 of 6Key terms
| Term | Meaning |
|---|---|
| Energy level | A region around the nucleus where an electron has a particular amount of energy. |
| Absorption | Taking in energy from radiation, which raises an electron to a higher level. |
| Emission | Giving out electromagnetic radiation when an electron drops to a lower level. |
| Frequency | The number of waves passing a point each second, measured in hertz (Hz). |
| Electromagnetic radiation | Waves, including light, that carry energy through space. |
Section 6 of 6Exam technique
1
Saying electrons absorb radiation and move closer to the nucleus. Absorption moves them further out.
2
Thinking emission happens as an electron moves up. Radiation is released when it falls back down.
3
Believing a bigger energy jump gives a lower frequency. A larger jump gives a higher frequency.
4
Writing that all atoms emit the same colours. The pattern of frequencies is specific to each element.