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.
📌 The Shell Rules
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.
Practice questions for Electronic Configuration
What is the maximum number of electrons the first electron shell can hold?
Explain why noble gases are unreactive.