Electrons are arranged in shells around the nucleus:
- 1st shell (closest to nucleus) — holds maximum 2 electrons
- 2nd shell — holds maximum 8 electrons
- 3rd shell — holds maximum 8 electrons (at GCSE level)
Filling order:
- Electrons always fill the lowest energy shell first (closest to nucleus)
- Only when a shell is full do electrons move to the next shell
- This is why electronic configuration follows predictable patterns!
Writing electronic configuration: Numbers separated by commas, e.g., 2,8,1 means 2 electrons in shell 1, 8 in shell 2, 1 in shell 3.
This key facts covers The Shell Rules within Electronic Configuration for GCSE Chemistry. Revise Electronic Configuration in Atomic Structure for GCSE Chemistry with 24 exam-style questions and 24 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 4 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Electronic Configuration
What is the maximum number of electrons the first electron shell can hold?
Explain why noble gases are unreactive.