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The Pauli exclusion principle states that two electrons can occupy the same orbital as long as they have opposite spin.
Hund's Rule states that the electrons fill the orbitals singly before pairing as this minimises repulsion and requires less energy. For neutral atoms the 4s orbital is of a slightly lower energy than the 3d orbital. This can change when ions are formed.
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Key terms in this lesson
- Ion
- A positively or negatively charged atom or group of atoms, formed by the loss or gain of electrons.
- Atomic orbital
- A region in space where there is a high probability (90-95%) of finding an electron.
More in Atoms, Ions and Compounds
- Calculating Relative Atomic Mass
- Chemical Formulae
- Polyatomic ions
- Chemical Equations
- Electron Shells
- Ionisation Energy
- Successive Ionisation Energies
- Trends in Ionisation Energy
All 17 lessons in Atoms, Ions and Compounds · All OCR AS-level Chemistry topics