Electron Structure
Chemistry: AQA GCSE Higher, topic 1.1.17
Electronic Structure
Electrons have fixed positions in atoms called shells or energy levels. These shells (or energy levels) go around the atom's nucleus.
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Filling electron shells
- Electrons fill an atom's shells in order of increasing energy.
- The closer a shell is to the nucleus, the lower its energy level, so the first shell that is filled is the closest to the nucleus.
Electron configuration
- Electron configuration tells us how an atom's electrons are organised.
- The inner shell (closest to the nucleus) can have a maximum of 2 electrons and the next two shells can have a maximum of 8 electrons.
- Any extra electrons are then put into a fourth shell.
Test yourself on Electron Structure
How many MORE electrons can fit in the 2nd electron shell compared to the 1st shell?
A phosphorus atom has 15 electrons and an electron configuration of 2, 8, 5. Why does the third shell contain only 5 electrons instead of the maximum of 8?
A calcium atom has 20 electrons and an electron configuration of 2, 8, 8, 2. Why does calcium's electron configuration include a fourth shell?
An argon atom has 18 electrons and an electron configuration of 2, 8, 8. Why does argon's configuration end at the third shell with no electrons in a fourth shell?