The coordination geometry of the complex formed between the lanthanide ion Europium III and the ligands 1,10-phenanthroline and pyridine depends on the stoichiometry of the ligands and the specific complex formed. However, Europium III typically forms complexes with coordination numbers of 8 or 9. In this case, let's assume a coordination number of 9.Considering the bidentate nature of 1,10-phenanthroline and the monodentate nature of pyridine, a possible complex could have three 1,10-phenanthroline molecules and three pyridine molecules coordinated to the Europium III ion. This would result in a coordination geometry of a tricapped trigonal prism.The oxidation state of the Europium ion in this complex would be +3, as indicated by the III notation in Europium III .