Explain Sidgwick's electronic theory with suitable examples.

Hint: We know that to solve this question we need to understand the basics of EAN rule. According to Sidgwick central metal ion effective Atomic Number i.e., EAN rule is the total number of electrons that surround the nucleus of an atom in a metal ion.

Complete answer:
The effective atomic number is a very common term used in the coordination chemistry branch. The effective number of chemistry can be represented as EAN chemistry inshort. Effective atomic number theory was the first theory that explained the concept behind the complex compound formation. This theory was given by Sidgwick.
Sidgwick's electronic theory states that the ligands donate the electron pair to the central metal ion and thus form a number of coordinate bonds. It donates one electron each for each carbonyl. So a total of three electrons are contributed. Sidgwick's electronic theory explains the formation of coordination compounds. Here, we need to understand that the oxidation number is the total number of electrons that are lost in iron formation and coordination number is the total number of electrons that are gained from the donor atoms. Sidgwick's electronic theory explains the formation of coordination compounds. According to this theory, coordinate bonds are formed when the ligands donate the electron pairs to the central metal ion.

Note:
Remember that we must know that the EAN rule is also referred to as the \[18-\] electron rule as the nine valences orbital can accommodate only \[18\] electrons. And also in coordination complexes, we can calculate the number of ligands that are attached to the central metal ion with the help of this theory.