Explain sidgwick's electronic theory with suitable example.

Explanation

Sidegwick's electronic theory or E.A.N. Rule : Sidewick suggested that the metal ion will continue accepting electron pairs till the total no. of electron in the metal ion and those donated by ligand is equal to the next higher nobel gas.
This total number of electron is called effective atomic number (EAN) of the metal.
`EAN =` Atomic number of the central metal `pm` the number of electrons gained or lost in ion formation + the number of electrons gained through coordination.
In rare cases, the metals may form a complex in its -ve oxidation state, that is why the sign `pm` is used here.
Example : Hexammine Rhodium (III) ion `[Rh(NH_(3))_(6)]^(3+)` in the present complex, Rhodium is present in oxidation state of `+3`
`:.` Total number of electrons in `Rh^(+3)=45-3=42`.
Since each `NH_(3)` ligand contributes two electrons to the Rhodium ion electrons contributed by `6 NH_(3)` ligands `=6xx2=12`
`:.` The EAN of `Rh^(+3)` is complex `=42+12=54`
In general,
EAN of metal = Atomic number - Oxidation state + coordination number `xx Z`
In this example since the number 54 correspond to atomic number of xenon, according to Sidegwick the complex will be stable.