Identify the oxidation state of the metal in each of the following compounds.
(a) (NH4)3[RhCl6]
(b) [Cr(NH3)4(SCN)2]Br
(c) [Cu(en)2]SO4
(d) Na2[Mn(EDTA)]

Verified step by step guidance

1. Identify the overall charge of the complex ion in each compound. For example, in (NH4)3[RhCl6], the ammonium ion (NH4+) has a charge of +1, and there are three ammonium ions, contributing a total charge of +3. The overall charge of the compound is neutral, so the complex ion [RhCl6] must have a charge of -3.
2. Assign oxidation states to the non-metal ions within the complex based on their common oxidation states. For instance, in [RhCl6]3-, each chloride ion (Cl) typically has an oxidation state of -1. With six chloride ions, the total charge contributed by the chloride ions is -6.
3. Calculate the oxidation state of the metal by balancing the total charge of the complex ion. The sum of the oxidation states of all components within the complex ion must equal the overall charge of the complex ion. For example, in [RhCl6]3-, if the chloride ions contribute -6, and the overall charge is -3, solve for the oxidation state of Rh.
4. Repeat the process for each compound. For [Cr(NH3)4(SCN)2]Br, first determine the charge of the complex ion [Cr(NH3)4(SCN)2]+ by considering the charge of the counter ion Br- which is -1. Then, assign oxidation states to SCN (thiocyanate) and NH3 (ammonia), which are typically -1 and 0, respectively.
5. For polydentate ligands like EDTA in Na2[Mn(EDTA)], recognize that EDTA usually forms a neutral complex with the metal ion. Calculate the oxidation state of Mn by considering the overall charge of the complex ion [Mn(EDTA)]2- and the charges of the sodium ions.

Key Concepts

Oxidation State

The oxidation state, or oxidation number, is a value that represents the total number of electrons an atom either gains or loses when it forms a compound. It helps in understanding the electron transfer in redox reactions and is crucial for determining the reactivity and stability of compounds. Oxidation states are assigned based on a set of rules, including the fact that the sum of oxidation states in a neutral compound must equal zero.

Coordination Compounds

Coordination compounds consist of a central metal atom bonded to surrounding molecules or ions, known as ligands. The nature of these ligands and their arrangement around the metal can influence the oxidation state of the metal. Understanding the structure and bonding in coordination compounds is essential for determining the oxidation states of the metal ions involved.

Common Ligands and Their Charges

Different ligands have specific charges that contribute to the overall charge of the coordination complex. For example, NH3 is a neutral ligand, while Cl- and SCN- are negatively charged. Knowing the charge of each ligand allows for the calculation of the oxidation state of the central metal by balancing the total charge of the complex with the charges of the ligands.