Question

Naming Compounds (When the Type Is Not Specified) Name each compound. (Refer to the nomenclature flowchart found in the Key Concepts section of the Chapter in Review.) $$a.\mathrm{SrCl}_{2} \quad b. \mathrm{SnO}_{2} \quad c. \mathrm{P}_{2} \mathrm{S}_{5}$$

Short answer

a. Strontium chloride b. Tin(IV) oxide c. Diphosphorus pentasulfide

Step-by-step solution

Identify the Type of the Compound for SrCl2

The compound SrCl2 contains a metal (Sr, strontium) and a nonmetal (Cl, chlorine). According to the nomenclature flowchart, this is an ionic compound with a metal forming a cation and a nonmetal forming an anion. The name of the metal is written first, followed by the nonmetal with the suffix -ide.

Name the Compound SrCl2

Strontium forms a +2 cation (Sr^{2+}) and chlorine forms a -1 anion (Cl^{-}). Since the metal is in its common oxidation state, we directly name it strontium. For the anion, we take the root of the nonmetal's name, chlorine, and add the suffix -ide, to get chloride. Therefore, SrCl2 is named as strontium chloride.

Identify the Type of the Compound for SnO2

The compound SnO2 consists of a metal (Sn, tin) and a nonmetal (O, oxygen). This is also an ionic compound, but since tin can have more than one possible charge, it is a Type II cation, so we need to specify the charge of tin in the name of the compound.

Name the Compound SnO2

Tin forms a +4 cation (Sn^{4+}) in this compound, as oxygen is typically -2 (O^{2-}) and there are two oxygen atoms to balance the +4 charge from tin. Hence, the compound is named tin(IV) oxide, where (IV) indicates the +4 oxidation state of tin.

Identify the Type of the Compound for P2S5

The compound P2S5 consists of two nonmetals, phosphorus (P) and sulfur (S). According to the flowchart for naming compounds, when two nonmetals form a compound, it is a covalent (molecular) compound and we use prefixes to denote the number of atoms of each element present in the compound.

Name the Compound P2S5

The prefixes for one to ten are mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and deca-. Since there are two atoms of phosphorus, we use the prefix di- for phosphorus. For sulfur, with five atoms, we use the prefix penta-. We do not use the prefix mono- for the first element. Therefore, P2S5 is named diphosphorus pentasulfide.

Key concepts

Ionic Compounds

Understanding ionic compounds is crucial in the world of chemistry. To put it simply, an ionic compound is formed when a metal and a nonmetal bond together. This bond is created due to the transfer of electrons from the metal to the nonmetal, which results in the metal becoming a positively charged ion, or cation, and the nonmetal becoming a negatively charged ion, or anion.

Let's look at an example from the exercise, strontium chloride (SrCl₂). Strontium (Sr), a metal, donates its electrons to chlorine (Cl), a nonmetal, forming Sr²⁺ and Cl⁻ ions. In naming ionic compounds, the metal (cation) is named first, followed by the nonmetal (anion) with an '-ide' suffix. Therefore, the correct name for SrCl₂ is strontium chloride, indicating a compound between the ions of strontium and chloride.

When dealing with ionic compounds involving a metal with variable charges, like tin (Sn), we must also specify the oxidation state of the metal. For example, SnO₂ is called tin(IV) oxide, where (IV) signifies the +4 oxidation state of tin.

Covalent Compounds

Moving on from ionic compounds, let's explore covalent compounds. Unlike ionic bonds, covalent bonds represent the sharing of electrons between two nonmetal atoms. This collaborative sharing creates a molecule, or a group of atoms tightly bound together.

In the context of covalent compounds, we use a specific naming system that incorporates prefixes to indicate the number of atoms of each element. For instance, the compound P₂S₅ comprises phosphorus (P) and sulfur (S). According to the prefixes, 'di-' refers to two, and 'penta-' signifies five. Thus, P₂S₅ is aptly named diphosphorus pentasulfide. Note that we don't use 'mono-' for the first element if there is only one atom of it. This system helps to precisely convey the number of each atom in a molecular compound.

Chemical Nomenclature

Delving into chemical nomenclature is essential for anyone looking to master chemistry. This system of rules applies to the naming of chemical compounds in a standardized manner. Understanding this system allows us to communicate the composition of compounds succinctly and across different languages and fields of science.

In the textbook exercise, we applied the nomenclature flowchart to name compounds systematically. With ionic compounds like SrCl₂ and SnO₂, the metal's name is stated first, followed by the nonmetal with 'ide' at the end, or by indicating the metal’s oxidation state if necessary. With covalent compounds like P₂S₅, we use prefixes such as 'di-' and 'penta-' to indicate the number of atoms present. These guidelines are invaluable for both beginners and seasoned chemists to avoid ambiguity and promote clear communication in chemistry.

Oxidation States

Finally, let's examine oxidation states, a fundamental concept tied deeply with chemical nomenclature. An oxidation state is an indicator of the degree of oxidation (loss of electrons) of an atom in a chemical compound. Understanding an element's oxidation state is vital, especially when dealing with transition metals that can possess multiple oxidation states.

For instance, in the name tin(IV) oxide (SnO₂), the Roman numeral IV indicates the oxidation state of tin, which is +4. The oxidation state plays a role in ensuring the charge balance of the compound, which is essential for the compound's stability. Since each oxygen atom has an oxidation state of -2, two oxygen atoms will balance out the +4 charge from tin. Recognizing oxidation states is not only important for naming compounds correctly but also for predicting their chemical behavior and properties.