What is the formula, including the charge, for each of the following complexes?
(a) An iridium(III) complex with three ammonia and three chloride ligands
(b) A chromium(III) complex with two water and two oxalate ligands
(c) A platinum(IV) complex with two ethylenediamine and two thiocyanate ligands

Verified step by step guidance

1. Identify the oxidation state of the central metal in each complex. For (a) iridium(III) indicates an oxidation state of +3 for iridium. For (b) chromium(III) indicates an oxidation state of +3 for chromium. For (c) platinum(IV) indicates an oxidation state of +4 for platinum.
2. Determine the charge contributed by each ligand. Ammonia (NH3) is a neutral ligand, contributing 0 charge. Chloride (Cl-) is an anionic ligand, contributing -1 charge per ligand. Water (H2O) is a neutral ligand. Oxalate (C2O4^2-) is an anionic ligand, contributing -2 charge per ligand. Ethylenediamine (en) is a neutral ligand. Thiocyanate (SCN-) can bind through either sulfur or nitrogen and is an anionic ligand, contributing -1 charge per ligand.
3. Calculate the total charge of the ligands for each complex. For (a), three chloride ligands contribute a total charge of -3. For (b), two oxalate ligands contribute a total charge of -4. For (c), two thiocyanate ligands contribute a total charge of -2.
4. Combine the charges of the central metal and the ligands to determine the overall charge of the complex. For (a), the total charge is +3 (from iridium) + (-3 from ligands) = 0. For (b), the total charge is +3 (from chromium) + (-4 from ligands) = -1. For (c), the total charge is +4 (from platinum) + (-2 from ligands) = +2.
5. Write the formula for each complex, including the charge. For (a), the formula is [Ir(NH3)3Cl3]. For (b), the formula is [Cr(H2O)2(C2O4)2]^-1. For (c), the formula is [Pt(en)2(SCN)2]^+2.

Key Concepts

Coordination Complexes

Coordination complexes consist of a central metal atom or ion bonded to surrounding molecules or ions known as ligands. The nature of these ligands, whether neutral or charged, influences the overall charge of the complex. Understanding how ligands coordinate to the metal is essential for determining the formula and charge of the complex.

Oxidation States

The oxidation state of a metal in a coordination complex indicates its charge and is crucial for writing the correct formula. For example, iridium(III) indicates that iridium has a +3 charge. Knowing the oxidation states of the metal and the charges of the ligands allows for accurate calculation of the overall charge of the complex.

Ligand Types and Charges

Ligands can be classified as neutral or charged, and their individual charges must be considered when determining the overall charge of the complex. For instance, ammonia is a neutral ligand, while chloride carries a -1 charge. Understanding the types of ligands and their respective charges is essential for constructing the correct chemical formula for the complexes.