Chemistry A-Level
sub-shell filling order
What sub-shell filling order means in Chemistry A-Level, as defined for AQA.
Definition of sub-shell filling order
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Reference: AQA
Electrons fill sub-shells in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p.
Topics that use sub-shell filling order
- Electron configuration (AQA A-Level)
Related terms
- 4s before 3d
- First ionisation energy
- Group 2 trend
- ion configurations
- ionisation equations
- orbital capacities
- Period 3 trend
Using sub-shell filling order in the exam
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