what is the difference between coordination entity and coordination sphere ?
In coordination compounds, the central metal atom alongwith the ions or ligands, attached to it are known as coordination entity. For example [CoCl3(NH3)3], the particles inside square bracket constitute the coordination entity.
Whereas, if enclose the coordiantion entity in square bracket, and indicate the net charge on the coordination entity, then it is known as coordination sphere. For example, [Fe(CN)6]4-, is the coordination sphere, with Fe(CN)6, as coordination entity.
Hope its clear now.