28.1.6—Why transition elements form complex ions
- Syllabus
- 9701–2028–2029
- Objective
- 28.1.6
- Level
- A2
Transition-metal complex ions form when ligand lone pairs donate into accessible metal orbitals
A complex ion contains a central metal ion surrounded by ligands. Empty or energetically accessible orbitals on the metal accept lone pairs to form coordinate (dative) bonds.
The metal charge, size and electron configuration influence ligand binding. Count donor atoms and show the overall charge rather than describing the complex as an ordinary ionic lattice.
[Cu(H₂O)₆]²⁺ forms when six water lone pairs coordinate to Cu²⁺.
A dative bond has both electrons from the ligand but is still a covalent bond once formed; it is not a simple ion pair.
ConceptA-Level CAIE Chemistry A2