EAN stands for Effective Atomic Number. It is a concept used in coordination chemistry to describe the effective charge on a central metal atom in a complex. In coordination compounds, a central metal atom or ion is surrounded by ligands, which are typically molecules or ions that donate electron pairs to form coordinate bonds with the central metal atom.
The Effective Atomic Number (EAN) is a theoretical concept that helps determine the number of electrons the central metal atom appears to have in its valence shell based on the coordination number and nature of the ligands. It is calculated by summing the valence electrons of the ligands and subtracting them from the valence electrons of the neutral metal atom.
If the EAN is equal to the valence electron count of the corresponding noble gas, the complex is considered stable. This is because the noble gas electron configuration represents a filled valence shell, which is a stable configuration for an atom.
The concept of EAN helps predict the stability and reactivity of coordination compounds and is often used in the design and analysis of transition metal complexes.