Question

Each of the following compounds has three possible names listed for it. For each compound, what is the correct name and why aren't the other names used? a. \(\mathrm{N}_{2} \mathrm{O}\) : nitrogen oxide, nitrogen(I) oxide, dinitrogen monoxide b. \(\mathrm{Cu}_{2} \mathrm{O}:\) copper oxide, copper(I) oxide, dicopper monoxide c. \(\mathrm{Li}_{2} \mathrm{O}:\) lithium oxide, lithium(I) oxide, dilithium monoxide

Short answer

The correct names for the given compounds are: a. Dinitrogen monoxide: the other names are incorrect as they either do not specify the number of atoms or inappropriately use oxidation states for nitrogen. b. Copper(I) oxide: transition metals like copper have different oxidation states, making it necessary to indicate the oxidation state. The other names either lack this detail or use inappropriate naming conventions. c. Lithium oxide: lithium has a fixed oxidation state of +1, making the use of Roman numerals unnecessary, and the IUPAC naming convention does not involve "di" or "mono" prefixes for such ionic binary compounds.

Step-by-step solution

a. Correct name for \(\mathrm{N}_{2} \mathrm{O}\)

The correct name for \(\mathrm{N}_{2} \mathrm{O}\) is dinitrogen monoxide. The reason behind this choice is that the IUPAC nomenclature rules for inorganic compounds require the use of prefixes denoting the number of atoms of each element present in the compound. In this case, we have two nitrogen atoms, thus the prefix "di" for nitrogen, and one oxygen atom, leading to the prefix "mono" for oxygen.

a. Incorrect names for \(\mathrm{N}_{2} \mathrm{O}\) and why

1. Nitrogen oxide: This name is incorrect because it does not specify the number of nitrogen and oxygen atoms, making it ambiguous. 2. Nitrogen(I) oxide: This name is not appropriate because the Roman numeral "(I)" represents the oxidation state of nitrogen. However, in this compound, nitrogen has an oxidation state of +1 while the other nitrogen has an oxidation state of -1, so using the oxidation state in the name would not be suitable here.

b. Correct name for \(\mathrm{Cu}_{2} \mathrm{O}\)

The correct name for \(\mathrm{Cu}_{2} \mathrm{O}\) is copper(I) oxide. Copper is a transition metal, and its compounds can have different oxidation states. In this case, copper has an oxidation state of +1 (due to only one oxygen atom), which is represented by the Roman numeral (I) in the compound's name.

b. Incorrect names for \(\mathrm{Cu}_{2} \mathrm{O}\) and why

1. Copper oxide: This name is incorrect because it does not indicate the oxidation state of copper, which is necessary for transition metal compounds. 2. Dicopper monoxide: This name would be used if Cu had a fixed oxidation state like Li in \(\mathrm{Li}_{2} \mathrm{O}\). However, it is not used in this context as copper has variable oxidation states, and the IUPAC naming convention relies on indicating the oxidation states of these elements.

c. Correct name for \(\mathrm{Li}_{2} \mathrm{O}\)

The correct name for \(\mathrm{Li}_{2} \mathrm{O}\) is lithium oxide. Lithium is an alkali metal, and it always has a fixed oxidation state of +1 in its compounds. In this compound, there are two lithium atoms, and they form an ionic bond with one oxygen atom, which has an oxidation state of -2. Since lithium only has one possible oxidation state, there is no need to include the oxidation state in the compound's name.

c. Incorrect names for \(\mathrm{Li}_{2} \mathrm{O}\) and why

1. Lithium(I) oxide: This name is incorrect because including the Roman numeral (I) is unnecessary, as lithium has only one possible oxidation state in its compounds, which is +1. 2. Dilithium monoxide: This name is not used because the IUPAC naming convention for ionic binary compounds formed by metals with a fixed oxidation state does not involve inserting "di" or "mono" prefixes for the involved elements.

Key concepts

Inorganic Chemistry

Inorganic chemistry is the branch of chemistry that deals with compounds lacking carbon-hydrogen bonds, encompassing a wide array of substances including minerals, metals, and organometallic compounds. It primarily involves the study of elements and compounds, devoid of carbon, and often involves elements across the periodic table, particularly metals and nonmetals.

Inorganic compounds are typically characterized by ionic bonding, where electrons are completely transferred from one atom to another. However, they can also exhibit covalent bonds, particularly in oxides and other nonmetal compounds. Understanding the specific properties of elements, such as their reactivity, electrochemical properties, and bonding patterns, is essential in developing an understanding of inorganic chemistry.

In the context of naming inorganic compounds, the International Union of Pure and Applied Chemistry (IUPAC) provides systematic rules ensuring predictability and consistency. These rules are based on a hierarchy of naming conventions allowing chemists to unambiguously identify compounds by name alone.

Oxidation States

Oxidation states, or oxidation numbers, are a conceptual tool used in chemistry to help track how electrons are transferred in chemical reactions and compounds. The oxidation state of an element in a compound provides insight into the distribution of electrons between that element and others in the compound.

Here's how oxidation states are determined and utilized:

• The oxidation state of a free element is always zero. For instance, in \( ext{N}_2\) or \( ext{Cu}_2\), the oxidation state of nitrogen or copper is zero.
• For a monoatomic ion, the oxidation state is equal to the ion's charge. For example, the Cl⁻ ion has an oxidation state of -1.
• The sum of oxidation states in a neutral compound is zero, while in a polyatomic ion it equals the ion's charge.

In transition metals like copper, multiple oxidation states are possible due to the involvement of d orbitals in bonding, allowing for complex ion formations. This is why specifying oxidation states in compound names is critical to avoid ambiguity. For example, copper(I) oxide indicates copper in a +1 oxidation state, whereas copper(II) oxide would indicate a +2 state. These numerical indicators are crucial for understanding not only the compound's structure but also its reactivity and properties.

Chemical Compounds Naming

Chemical compounds naming, also known as chemical nomenclature, is a critical aspect of chemistry that allows scientists to communicate complex compositions and structures with precision. The IUPAC system is the most widely accepted standard for naming chemical compounds, ensuring uniformity across the scientific community.

There are several principles involved in naming chemical compounds, particularly inorganic ones:

• Binary compounds: These consist of two elements and are named with the more electropositive (or metallic) element first. For instance, in \( ext{Li}_2 ext{O}\), lithium comes before oxygen, resulting in lithium oxide.
• Use of prefixes: For molecular compounds, prefixes like "di-", "tri-", and "mono-" indicate the number of atoms present. For \( ext{N}_2 ext{O}\), the correct name is dinitrogen monoxide, indicating two nitrogen atoms.
• Oxidation states: For metals, especially transition metals, Roman numerals are used to indicate oxidation states, like in copper(I) oxide. This avoids confusion with other possible states the metal might assume.

Adhering to these guidelines is essential for accurately describing compounds and inferring their chemical behavior. Proper chemical naming also facilitates understanding across diverse fields of chemistry, underpinning research, teaching, and industrial applications.