Complex Ions

Complex Ions are Metal Ions Surrounded by Ligands

A complex is a metal ion surrounded by coordinately bonded ligands.

• A coordinate bond is a covalent bond in which both electrons in the shared pair come from the same atom. In a complex, they come from ligands.
• So, a ligand is an atom, ion or molecule that donates a pair of electrons to a central metal ion. 
• The coordination number is the number of coordinate bonds that are formed with the central metal ion.
• The usual coordination numbers are 6 and 4. If the ligands are small, like H2O or NH3, 6 can fit around the central ion. But if the ligands are larger, like Cl-, only 4 can fit around…