Unit 1 · Atomic Structure
Electron Configuration
Orbitals, sub-shells and how electron arrangement explains periodic behaviour.
AS2 lessonsPublished
Lessons
Lessons in this topic
Published
Orbitals and Sub-shells
What s, p and d sub-shells actually represent, and how to write electron configurations without memorizing them.
- Electrons occupy orbitals — regions of space where an electron is most likely to be found.
- Sub-shells fill in order of increasing energy, which is why 4s fills before 3d.
- Configuration explains ionisation energy patterns rather than the other way round.
Published
Ionisation Energy Trends
Using nuclear charge, shielding and distance to reason through every ionisation energy question.
- Three factors control ionisation energy: nuclear charge, shielding and atomic radius.
- Successive ionisation energies reveal shell structure.
Resources
Practise this topic
NotesStandard
AS Atomic Structure — Concept Notes
Condensed notes covering subatomic particles, isotopes and electron configuration.
A Level Chemistry · AS