Stability Constant
The equilibrium constant for the formation of a complex ion from its metal ion and ligands.
Formula / equation
K = [MLₙ] / ([M][L]ⁿ)
Unit
Various
In depth
Also called the formation constant, a large value indicates a very stable complex with a vanishingly small free metal ion concentration. Stability rises with ligand denticity, with metal ion charge and with the softness match between metal and donor atom.
Examples in the real world
[Cu(NH₃)₄]²⁺ has a stability constant near 10¹³; the EDTA complex of Ca²⁺ is about 10¹⁰·⁷.