Write the formula for each complex ion or coordination compound. a. hexaamminechromium(III) b. potassium hexacyanoferrate(III) c. ethylenediaminedithiocyanatocopper(II) d. tetraaquaplatinum(II) hexachloroplatinate(IV)

Complex ion chemistry is a fascinating topic that deals with the structures and reactions of complex ions. These ions consist of a central metal atom or ion surrounded by molecules or anions called ligands. The central metal is called the coordination center, and can form coordinate bonds with the ligands through its empty orbitals.

In understanding complex ion chemistry, one must recognize how the ligands donate pairs of electrons to the metal, creating a coordination complex. The number of atoms or ions surrounding the central metal is known as the coordination number, and it can vary depending on the size and electronic configuration of the metal and the ligands. Certain rules govern the naming and formula writing of these compounds, which involve the use of specific nomenclature to accurately describe their composition.

For example, in a compound named 'hexaamminechromium(III)', 'hexa-' indicates the presence of six ammonia ligands while 'chromium(III)' denotes the central metal and its oxidation state. An important aspect of complex ions is their ability to exist as charged entities within salts or as neutral species, leading to a vast array of chemical behavior and applications in various fields such as biochemistry, medicine, and materials science.

Identification of oxidation states in coordination compounds is crucial for understanding their chemical properties. The oxidation state, often represented by a Roman numeral, indicates the charge on the central metal atom after hypothetically all the ligands have been removed along with the electrons they shared with the metal.

Oxidation state helps predict the reactivity and bonding nature of the metal within the complex. To determine the oxidation state, one must consider the overall charge of the complex and the charge associated with each ligand. For instance, in the compound 'potassium hexacyanoferrate(III)', the Roman numeral '(III)' signifies an oxidation state of +3 for the iron metal ion. By knowing the charge contributed by each cyanide ligand (each -1), one can then deduce the necessity of a counter ion, potassium (K+), to balance the overall charge of the complex.

Steps to Identify Oxidation States:

• Review the formula and recognize the central metal atom.
• Examine the given Roman numeral indicating the metal's oxidation state.
• Calculate the total charge contributed by the ligands.
• Balance the charge with either counter ions or the central metal's oxidation state as needed.

Understanding oxidation states is fundamental when exploring the reactivity, color, magnetic properties, and other characteristics of coordination compounds.

Ligands are essential components of coordination compounds, acting as the 'arms' that embrace the central metal atom or ion. They can be neutral molecules like water (H₂O) or ammonia (NH₃), or anions like chloride (Cl^-) or cyanide (CN^-). When naming coordination compounds, ligands are listed before the central metal, with specific prefixes used to denote the number of each type of ligand.

Common Prefixes:

• mono- for one ligand
• di- for two ligands
• tri- for three ligands
• tetra- for four ligands
• penta- for five ligands
• hexa- for six ligands

It's important to use these prefixes correctly when writing the formula of a coordination compound. For example, in 'tetraaquaplatinum(II) hexachloroplatinate(IV)', 'tetra-' indicates that there are four water ligands coordinated to the central platinum ion, whereas 'hexa-' represents six chloride ligands in the second part of the molecule. Such precise terminology not only allows chemists to communicate effectively but also provides clues to the geometric structure of the complex itself.