K₃[Al(C₂O₄)₃] is called

Potassium trioxalatoaluminate (III)

Explanation:

• Identification of Ions:
  • Cation: Three potassium ions (K⁺).
  • Anion: The complex ion [Al(C₂O₄)₃]³⁻.
• Naming the Complex Ion:
  • Ligand: The oxalate ion (C₂O₄²⁻) is a bidentate ligand, named as 'oxalato'.
  • Quantity of Ligands: Three oxalate ligands are present, denoted by the prefix 'tri'.
  • Central Metal Ion: Aluminum (Al) in an anionic complex is named 'aluminate'.
  • Oxidation State: The oxidation state of aluminum is +3, represented as '(III)'.
• Constructing the Name:
  • Cation: 'Potassium'
  • Anion: 'Trioxalatoaluminate (III)'
  • Full Name: Potassium trioxalatoaluminate (III).

Oxidation State Calculation:

• Oxalate Ligand Charge: Each oxalate ion carries a charge of -2.
• Total Charge from Ligands: 3 × (-2) = -6.
• Overall Complex Charge: -3.
• Aluminum Oxidation State (x):
  • x + (-6) = -3
  • x - 6 = -3
  • x = +3

Therefore, the oxidation state of aluminum in this compound is +3.