BRAINCAKEFilling of Orbitals and Electron Pairing
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
- Atomic number
- The number of protons in the nucleus of an atom.
- Atomic orbital
- A region in space where there is a high probability (90-95%) of finding an electron.
- Electron configuration
- The notation showing the arrangement of an atom's electrons in shells and sub-shells, such as 1s2 2s2 2p6.
More in Electrons and Bonding
- Electron Structure
- Ionic Bonding
- Structure and Properties of Ionic Compounds
- Covalent Bonding
- Single, Double and Triple Bonds
- Dative Covalent Bonds
All 7 lessons in Electrons and Bonding · All OCR AS-level Chemistry topics