Problem 41 - Chemistry: An Atoms-Focused Approach

Question

What are the names of the following compounds? (a) MnS; (b) \(\mathrm{V}_{3} \mathrm{N}_{2} ;\) (c) \(\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3} ;\) (d) \(\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{2} ;\) (e) \(\mathrm{Fe}_{2} \mathrm{O}_{3}\)

Step-by-Step Solution

Answer

(a) MnS, (b) V₃N₂, (c) Cr₂(SO₄)₃, (d) Co(NO₃)₂, (e) Fe₂O₃. Answer: The names of the given compounds are: (a) manganese(II) sulfide, (b) vanadium(III) nitride, (c) chromium(III) sulfate, (d) cobalt(II) nitrate, and (e) iron(III) oxide.

Step 1: (a) MnS

MnS is an ionic compound formed between manganese (Mn) and sulfur (S). Manganese has an oxidation state of +2 (Mn\(^{2+}\)) and sulfur has an oxidation state of -2 (S\(^{2-}\)). The compound's name is manganese(II) sulfide.

Step 2: (b) V\(_3\)N\(_2\)

V\(_3\)N\(_2\) is an ionic compound formed between vanadium (V) and nitrogen (N). To determine the oxidation state of vanadium in the compound, we use the general formula for ionic compounds: x * number of cations + y * number of anions = 0. In this case, we have 3 * x + (-3) * 2 = 0. Solving for x, we find that vanadium has an oxidation state of +3 (V\(^{3+}\)). The compound's name is vanadium(III) nitride.

Step 3: (c) Cr\(_2\)(SO\(_4\))\(_3\)

Cr\(_2\)(SO\(_4\))\(_3\) is an ionic compound formed between chromium (Cr) and the sulfate ion (SO\(_4^{2-}\)). In this case, we have 2 * x + (-2) * 3 = 0. Solving for x, we find that chromium has an oxidation state of +3 (Cr\(^{3+}\)). The compound's name is chromium(III) sulfate.

Step 4: (d) Co(NO\(_3\))\(_2\)

Co(NO\(_3\))\(_2\) is an ionic compound formed between cobalt (Co) and the nitrate ion (NO\(_3^{-}\)). In this case, we have x + (-1) * 2 = 0. Solving for x, we find that cobalt has an oxidation state of +2 (Co\(^{2+}\)). The compound's name is cobalt(II) nitrate.

Step 5: (e) Fe\(_2\)O\(_3\)

Fe\(_2\)O\(_3\) is an ionic compound formed between iron (Fe) and oxygen (O). To determine the oxidation state of iron in the compound, we use the general formula for ionic compounds: x * number of cations + y * number of anions = 0. In this case, we have 2 * x + (-2) * 3 = 0. Solving for x, we find that iron has an oxidation state of +3 (Fe\(^{3+}\)). The compound's name is iron(III) oxide.

Key Concepts

Oxidation States

In chemistry, oxidation states are essential for understanding the formation of ionic compounds. An oxidation state represents the degree of oxidation or the hypothetical charge an atom would have if all bonds were ionic.
The concept is widely used for categorizing elements, especially in coordination compounds.
Each element in a compound influences the oxidation states of the other atoms.

• For instance, in MnS, the manganese (Mn) has an oxidation state of +2, while sulfur (S) has an oxidation state of -2.
• This means manganese donates two electrons to sulfur, forming an ionic bond.
• Similarly, in V e 3N e 2, vanadium's +3 oxidation state balances the -2 charge per nitrogen atom.

Recognizing oxidation states allows chemists to determine the proper name of the compound, ensuring it reflects the actual chemical structure. It is the key to naming transition metal compounds, where metals can have various oxidation states.

Chemical Nomenclature

Chemical nomenclature is the system used to name chemical compounds. It is an organized way to ensure each compound has a unique name that provides insight into its chemical makeup.
IUPAC, the International Union of Pure and Applied Chemistry, is the authority that sets these naming standards.

• For ionic compounds, the metal is named first followed by the non-metal with its name modified to end in "-ide," like manganese(II) sulfide (MnS).
• When dealing with transition metals, include the oxidation state in Roman numerals in parentheses. This clarifies, for example, that in chromium(III) sulfate, chromium has a +3 oxidation state.

By following these standardized rules, one can deduce information about a compound's composition just from its name, aiding in better understanding and communication of chemical information.

Transition Metals

Transition metals occupy the central block of the periodic table, specifically groups 3 to 12. They are distinguished by their ability to form compounds with varying oxidation states.
This flexibility is because their d-orbitals allow for different configurations of electron sharing and donation.

• Transition metals can form colorful compounds, each hue indicating different oxidation states or ligand fields.
• They typically engage in complexation reactions, which involve forming compounds where metal ions are bonded to several molecules or ions.
• Their ability to switch oxidation states makes them excellent catalysts in industrial processes and biological systems.

Examples from the exercises, such as iron in iron(III) oxide, showcase their typical behavior.
Due to their wide range of chemical properties, transition metals are crucial in various applications from construction to electronic devices and even quantum computing.
These metals demonstrate why understanding oxidation states and chemical nomenclature is vital for practical chemistry.