BRAINCAKEElectronic Configurations
Orbitals fill in order of increasing energy.
The order of filling is:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p
The 4s orbital is filled before the 3d orbital as the 3d orbital has a higher energy than the 4s orbital.
Each orbital can hold up to 2 electrons as long as they have opposite spins.
The opposite spin helps to counteract the repulsion between electrons in the same orbital. Orbitals with the same energy are occupied singly and then paired when there is no unoccupied orbital left.
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Key terms in this lesson
- orbital
- A region around a nucleus that can hold up to two electrons of opposite spin.
More in Atomic Structure
- Relative Atomic Mass from a Mass Spectrometer
- Relative Molecular Mass from a Mass Spectrometer
- Quantum Shells
- Orbitals
- Predicting Electronic Configuration
- Energy Levels and Emission Spectra
- First Ionisation Energy
- Successive Ionisation Energies
All 19 lessons in Atomic Structure · All Edexcel AS-level Chemistry topics