what is the formula of the complex ion formed between water, the ligand, and Cu^2+, Co^3+, Ni^2+
The reaction is:
Cr₃⁺ +3 C₁₀H₈N₂ → [Cr(C₁₀H₈N₂)₃]³⁺
2,2\'-bipyridine is bidentate ligand and neutral. It exhibits two N terminal, thus, it functions as bidentate ligand.
Therefore, three 2,2\'-bipyridine ligand fulfills the six coordination number of Cr₃⁺.
The formula for the complex is [Cr(C₁₀H₈N₂)₃]³⁺