Transition metals form complex ions because of their partially filled d-orbitals and ability to accept electron pairs from ligands. Here’s a explanation:
1. Availability of empty orbitals
- Transition metals have empty or partially filled d-orbitals.
- These orbitals can accept lone pairs of electrons from ligands to form coordinate covalent bonds.
2. Stability of complexes
- Forming a complex stabilizes the metal ion by surrounding it with ligands.
- This helps reduce the high charge density on small, highly charged metal ions.
3. Versatility of bonding
- Transition metals can form complexes with neutral ligands (like H₂O, NH₃) or anionic ligands (like Cl⁻, CN⁻).
- They can have different coordination numbers, commonly 4 or 6, depending on the size and charge of the metal.
4. Example in words
- Iron(III) in water forms [Fe(H₂O)₆]³⁺, where six water molecules surround and bond to the Fe³⁺ ion.
In short:
Transition metals form complex ions because their d-orbitals can accept electron pairs from ligands, forming stable coordination compounds.