Case: Read the passage and answer the following questions

The naming of mononuclear coordination compounds follows some rules. Cations are always named before the anions. The ligands are then listed in alphabetical order. In the case of polydentate ligands, ligands are named alphabetically using the prefix di, tri, tetra, Penta etc, to indicate the number of ligands of that type present.

What is the formula of the compound Potassium trioxalatoaluminate(III)?

K₃[Al(C₂O₄)₃]

Oxalate ion has −2 charge. 3 oxalate ions have −2×3=−6 charge which is balanced with +3 charge on one Al ion and +3 charge on 3 K ions (each K ion has +1 charge)

K₃[Al(C₂O₄)₃] → 3K⁺ + [Al(C₂O₄)₃]^3- 

In [Al(C₂O₄)₃]^3-  

x + 3(-2) = -3

x - 6 = -3

x = -3 + 6 = 3

Al³⁺