Pairing Energy
Definition and meaning of Pairing Energy in chemistry.
Pairing energy is the specific amount of thermodynamic energy required to force two electrons to occupy the exact same orbital despite their inherent mutual electrostatic repulsion.
In more detail
In the context of crystal field theory, this pairing energy directly opposes the crystal field splitting energy when determining the final electron configuration of transition metal complexes. If the splitting energy caused by the ligands is significantly greater than the pairing energy, electrons prefer to pair up in lower energy orbitals, forming a low-spin complex. Conversely, if the pairing energy is greater, a high-spin complex forms as electrons instead occupy higher energy orbitals to avoid the energetic penalty of pairing.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Formula | [Fe(CN)6] 4- |
| Opposing factor | Crystal field splitting energy |
| Resulting chemical states | High-spin or low-spin metal complexes |
In the hexacyanoferrate(II) ion, [Fe(CN)6] 4-, the strongly interacting cyanide ligand causes a massive crystal field splitting that far exceeds the pairing energy, resulting in a low-spin complex.
Frequently asked questions
How exactly does pairing energy dictate the magnetic properties of a transition metal complex?
It determines whether electrons will pair up in lower d-orbitals (creating diamagnetic low-spin complexes) or occupy higher d-orbitals singly (creating paramagnetic high-spin complexes).