Question

Name the following ions or compounds: (a) \(\mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_{4}\right]\) (b) \(\left[\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)^{-}\right]\) (c) \(\left[\operatorname{Ir}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]\) (d) \(\left[\mathrm{Cr}(e n)\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Br}_{2}\right]_{2} \mathrm{SO}_{4}\)

Short answer

Short Answer: Four ions or compounds and their respective names are (a) sodium tetrahydroxidoaluminate, (b) diaquabis(oxalato)cobaltate(III), (c) trichlorotriammineiridium(III), and (d) diammobis(bromo)(ethylenediamine)chromium(III) sulfate.

Step-by-step solution

(a) Naming the ion of Na[Al(OH)4]

The given ion consists of a sodium cation, Na+, and a complex anion formed from aluminum and hydroxide groups: [Al(OH)4]-. To name this ion, first, we name the cation, which is "sodium". Then, we name the complex anion as follows: The complex anion consists of an aluminum atom as the central atom and four hydroxide groups bound to it. The name of the complex anion will be "tetrahydroxidoaluminate" (tetra- means four, hydroxido- refers to the hydroxide ligand and aluminate refers to the aluminum atom). The name of the ion is: sodium tetrahydroxidoaluminate.

(b) Naming the complex ion of [Co(C2O4)2(H2O2)-]

The given complex ion consists of a cobalt atom as the central atom, two oxalate ligands (C2O4)2-, two water molecules as ligands, and has a negative charge. To name this ion, we follow the rules: 1. Name the ligands in alphabetical order (oxalate and aqua, not considering the prefix). 2. Use the prefix di- for ligands that appear twice. 3. Name the central atom (cobalt) and add the oxidation state in Roman numerals. 4. Since it's an anion, add suffix -ate. The name of the complex ion is: diaquabis(oxalato)cobaltate(III).

(c) Naming the complex of [Ir(NH3)3Cl3]

The given complex consists of an iridium atom as the central atom, three ammonia (NH3) molecules and three chloride (Cl-) ions as ligands. To name this compound, we follow these rules: 1. Name the ligands in alphabetical order (ammonia and chloro). 2. Use the prefix tri- for ligands that appear three times. 3. Name the central atom (iridium) and add the oxidation state in Roman numerls. The name of the complex is: trichlorotriammineiridium(III).

(d) Naming the complex of [Cr(en)(NH3)2Br2]2SO4

The given compound contains a complex cation [Cr(en)(NH3)2Br2]2+ and a sulfate anion (SO4)2-. To name this compound, we first name the complex cation and then the anion. 1. Name the ligands in alphabetical order (ammine, bromo, ethylenediamine) 2. Use the prefix di- for ligands that appear twice. 3. Name the central atom (chromium) and add the oxidation state in Roman numerals. 4. Name the anion (sulfate). The name of the compound is: diammobis(bromo)(ethylenediamine)chromium(III) sulfate.

Key concepts

Coordination Chemistry

Coordination chemistry is a branch of inorganic chemistry that deals with the study of compounds featuring coordination complexes. These are structures where a central metal atom or ion is surrounded by molecules or anions, known as ligands. The metal and ligands are held together by coordination bonds, which involves the sharing of electron pairs between the ligand and the metal center.

These complexes can exhibit a vast array of chemical behaviors and can be found in various applications such as catalysis, electronic materials, and even in biological systems where metalloproteins contain these central structures. The central metal atom can have different oxidation states, which is integral to the compound's reactivity and properties. Identifying the oxidation state is equally crucial when it comes to naming these compounds.

Nomenclature of Inorganic Compounds

The oxidation state, often called oxidation number, is a key concept in coordination chemistry that describes the degree of oxidation of an atom in a chemical compound. It is indicated with Roman numerals in parentheses right after the metal's name in the compound. Understanding the metal's oxidation state is essential because it can impact the compound's color, magnetic properties, reactivity, and stability.

An atom's oxidation state is determined based on a set of rules, which consider the electronegativity of the atoms involved and the electron distribution in chemical bonds. In naming compounds, the oxidation state can help distinguish between compounds that have the same composition but different structural arrangements. It is thus indispensable for accurately conveying the structure of coordination compounds.

Ligands

When naming coordination compounds like those in the original exercise, students often find the varying ligand names, the ordering of words, and the inclusion of oxidation states to be quite challenging. Special attention to the specific prefixes and the alphabetical order of ligands, irrespective of their quantity, are common stumbling blocks. Therefore, it is important to reiterate that ligands are named first, followed by central metal and oxidation state, and that detailed rules must be followed for a correct naming convention.

It's essential for students to grasp these concepts for accurate chemical communication and also for understanding the nature and functionality of inorganic compounds in real-world applications such as medicinal chemistry and materials science.