![]() ![]() The two examples mentioned in the previous paragraph are represented by the formulasįigure 2.32 (a) Erin Brockovich found that Cr(VI), used by PG&E, had contaminated the Hinckley, California, water supply. Washing soda is the common name for a hydrate of sodium carbonate containing 10 water molecules the systematic name is sodium carbonate decahydrate.įormulas for ionic hydrates are written by appending a vertically centered dot, a coefficient representing the number of water molecules, and the formula for water. ![]() The added word begins with a Greek prefix denoting the number of water molecules (see Table 2.10) and ends with “hydrate.” For example, the anhydrous compound copper(II) sulfate also exists as a hydrate containing five water molecules and named copper(II) sulfate pentahydrate. The name for an ionic hydrate is derived by adding a term to the name for the anhydrous (meaning “not hydrated”) compound that indicates the number of water molecules associated with each formula unit of the compound. Ionic compounds that contain water molecules as integral components of their crystals are called hydrates. The other fluoride of tin is SnF 4, which was previously called stannic fluoride but is now named tin(IV) fluoride. This represents the formula SnF 2, which is more properly named tin(II) fluoride. For example, you may see the words stannous fluoride on a tube of toothpaste. Though this naming convention has been largely abandoned by the scientific community, it remains in use by some segments of industry. Out-of-date nomenclature used the suffixes – ic and – ous to designate metals with higher and lower charges, respectively: Iron(III) chloride, FeCl 3, was previously called ferric chloride, and iron(II) chloride, FeCl 2, was known as ferrous chloride. Other examples are provided in Table 2.9. These two compounds are then unambiguously named iron(II) chloride and iron(III) chloride, respectively. In cases like this, the charge of the metal ion is included as a Roman numeral in parentheses immediately following the metal name. The simplest name, “iron chloride,” will, in this case, be ambiguous, as it does not distinguish between these two compounds. Iron typically exhibits a charge of either 2+ or 3+ (see Figure 2.29), and the two corresponding compound formulas are FeCl 2 and FeCl 3. For example, consider binary ionic compounds of iron and chlorine. The charge of the metal ion is determined from the formula of the compound and the charge of the anion. ![]() Compounds of these metals with nonmetals are named with the same method as compounds in the first category, except the charge of the metal ion is specified by a Roman numeral in parentheses after the name of the metal. Most of the transition metals and some main group metals can form two or more cations with different charges. Table 2.8 Compounds Containing a Metal Ion with a Variable Charge The name of a binary compound containing monatomic ions consists of the name of the cation (the name of the metal) followed by the name of the anion (the name of the nonmetallic element with its ending replaced by the suffix – ide). First, is the compound ionic or molecular? If the compound is ionic, does the metal form ions of only one type (fixed charge) or more than one type (variable charge)? Are the ions monatomic or polyatomic? If the compound is molecular, does it contain hydrogen? If so, does it also contain oxygen? From the answers we derive, we place the compound in an appropriate category and then name it accordingly. To name an inorganic compound, we need to consider the answers to several questions. The rules for organic compounds, in which carbon is the principle element, will be treated in a later chapter on organic chemistry. We will limit our attention here to inorganic compounds, compounds that are composed principally of elements other than carbon, and will follow the nomenclature guidelines proposed by IUPAC. The simplest of these are binary compounds, those containing only two elements, but we will also consider how to name ionic compounds containing polyatomic ions, and one specific, very important class of compounds known as acids (subsequent chapters in this text will focus on these compounds in great detail). This module describes an approach that is used to name simple ionic and molecular compounds, such as NaCl, CaCO 3, and N 2O 4. Nomenclature, a collection of rules for naming things, is important in science and in many other situations. Derive names for common types of inorganic compounds using a systematic approach.By the end of this section, you will be able to:
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