Amongst the following, identify the species with an atom in \(+6\) oxidation state: (a) \(\mathrm{MnO}_{4}^{-}\) (b) \(\mathrm{Cr}(\mathrm{CN})_{6}^{3-}\) (c) \(\mathrm{NiF}_{6}^{2}\) (d) \(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\)

Chemical bonding is a fundamental concept in chemistry that involves the joining of atoms to form molecules and compounds. At its core, bonding is about the exchange or sharing of electrons between atoms. There are three main types of chemical bonds: ionic, covalent, and metallic.

Ionic bonding occurs when atoms transfer electrons from one to another, resulting in positively and negatively charged ions that attract each other. In the exercise option (d) \(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\), the chromium atom is involved in ionic bonding with oxygen and chlorine atoms. Here, electron transfer is not complete because real-world bonding is often not purely ionic; it has some covalent character as well.

Covalent bonding, on the other hand, involves the sharing of electron pairs between atoms. This type of bond usually forms between non-metal atoms with similar electronegativities. In the example of the cyanide ion \(\mathrm{CN}^{-}\), present in option (b), carbon and nitrogen share a pair of electrons, forming a covalent bond. Understanding the types of chemical bonds is crucial when determining oxidation states, as each bond type can influence the electron distribution in a compound.

Redox reactions are a family of chemical reactions that involve the transfer of electrons between two species. The term 'redox' is a shorthand reference for reduction-oxidation reactions. In such reactions, one species undergoes oxidation by losing electrons, while another undergoes reduction by gaining electrons. The oxidation states of atoms involved in redox reactions change, as reflected in the exercises provided.

The oxidation state is a helpful number that lets us use the concept of electrons to balance redox equations. Identifying the right oxidation state, as in the given exercise, is central for understanding redox processes. For example, in option (d) \(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\), the chromium (Cr) atom has an oxidation state of +6. This information can inform us about the possible redox reactions chromium can participate in, such as being reduced to a lower oxidation state in a chemical process. The systematic approach to determining the oxidation state involves considering the known states of other atoms (like the -2 for oxygen and -1 for chlorine) and the overall charge of the molecule or ion.

Coordination chemistry is a branch of chemistry that focuses on complex compounds formed between metal ions and ligands. Ligands are ions or molecules that can donate pairs of electrons to a metal ion, forming a coordination complex. For instance, in option (b) \(\mathrm{Cr}(\mathrm{CN})_{6}^{3-}\), chromium (Cr) forms a coordination complex with cyanide (CN) ligands. The number of ligands attached to the metal, known as the coordination number, is an important aspect to consider.

In coordination compounds, the oxidation state of the metal ion is particularly significant because it affects the compound's properties and reactivity. Understanding how to find the oxidation state of a metal in a complex, as done for chromium (Cr) in option (b), is critical for predicting the behavior of the complex in various chemical reactions. Additionally, the arrangement of ligands around the metal ion, known as the coordination geometry, determines the physical and chemical properties of the complex. Coordination chemistry principles also explain how certain ligands like \(\mathrm{CN}^{-}\) can alter the metal's ability to engage in redox reactions, highlighting an overlap with the concept of redox reactions.