D-block elements form coordination compounds because they have empty or partially filled d-orbitals that can accept electron pairs from other atoms or molecules. Here’s a explanation:
1. Role of Metal Ions
- The central metal ion in d-block elements can act as an electron-pair acceptor (Lewis acid).
- Its partially filled d-orbitals allow it to bond with ligands.
2. Role of Ligands
- Ligands are atoms, ions, or molecules that have lone pairs of electrons.
- They donate these electrons to the metal ion to form coordinate bonds.
- Example of ligands: Water, ammonia, cyanide, chloride.
3. Formation of the Complex
- The metal ion surrounded by ligands forms a coordination compound.
- The number of ligands attached is called the coordination number (usually 4 or 6).
4. Stability
- The d-orbitals of the metal help stabilize the compound by sharing electrons with ligands.
- Some complexes are very stable due to chelation, where a ligand binds at multiple points.
5. Examples
- [Fe(CN)₆]³⁻ – Iron forms a complex with cyanide ligands.
- [Cu(NH₃)₄]²⁺ – Copper forms a complex with ammonia ligands.
In short:
D-block elements form coordination compounds because their d-orbitals can accept electron pairs from ligands, creating stable complexes.