Draw the structures of geometrical isomers of the following coordination complexes:
[Co(NH₃)₃Cl₃] and [CoCl₂(en)₂⁺]
(en = ethylene diamine and atomic number of Co is 27).   

Illustrate with an example of the following:
Linkage isomerism

(i) Explain geometrical isomerism with reference to square planar complexes giving one example. How is tetrahedral complexes with simple ligands do not exhibit geometrical isomerism?
(ii)    Using valence bond theory, predict the shape and magnetism (paramagnetism) or diamagnetism of [Co(CO)₄]^– (at. no. of Co = 27)?
(iii)    How is stability of coordination compounds determined in aqueous solution?

229. In [Co(C₂O₄)₃]^3–, the coordination number of cobalt is ________.