Nomenclature 1 Naming Binary Compounds

During Werner s time compositional nomenclature for binary compounds had already been agreed upon in much the same way as today, and names such as manganese dichloride and manganese monooxide were in common use to express information about stoichiometric compositions only. For complex compounds, this type of nomenclature had simply b n extended as in the notational example 3 KCN,Fe(CN)3. Werner realized that diis notation could be modified to became a nomenclature including structural information, when this was available, and potassium hexacyanoferriate is his ingenious proposal (2). This is an example of what is today referred to as additive nomenclature or coordination nomenclature, as opposed to the substitutional nomenclature of organic chemistry. 

Some compounds, namely molecular compounds, contain only nonmetals. Normally the compounds you need to name are binary compounds (containing only two elements). If you have highlighted the metalloids on your periodic table, everything to the right of the metalloids is a nonmetal. The following rules apply to both nonmetals and metalloids. The only nonmetal excluded from these nomenclature rules is hydrogen. 

Many hydrogen compounds are acids. Acids require a different system of nomenclature than other compounds. There are two types of acids binary acids and ternary acids. All acids include the word acid in their name. Binary acids contain only two elements one of which is hydrogen and the other a nonmetal. When naming binary acids, the prefix hydro- appears before the root name of the nonmetal, and there will be an -ic suffix. As an acid, H2S would be hydrosulfuric acid. We used H2S to illustrate the fact that there can be two possible names, hydrogen sulfide or hydrosulfuric acid. If your instructor does not specify which name to use, either is correct. Technically, the name hydrosulfuric acid only applies to aqueous solutions of H2S, H2S(aq). 

This provides names for compounds for which little or no structural information is available. However, a minimum of structural information is known or assumed. In particular, using the assumed or established division of constituents into positive and negative parts already employed above in establishing formulae, we divide the constituents into the same two classes, hence the term binary nomenclature . 

Additive nomenclature1 is based on the combination of element names or roots of element names and/or ligand names. The simplest and oldest additive nomenclature is binary nomenclature that expresses two components, e.g. sodium chloride. The cationic or electropositive portion of the compound expressed in a binary name is the element name unchanged or a group name ending in -ium , and the anionic or electronegative portion of a compound expressed in the name ends in -ide, -ite or -ate. The proportions of cations and anions in neutral compounds are indicated by Stock numbers or simple or multiplicative prefixes (see Section 3.3.2). Additive nomenclature denotes composition. For examples see Table 1. 

Nomenclature of Salts. — Salts containing only two elements follow the rule for binary compounds, aiid hence end in -ide. This suffix is added to an abbreviated form of the name of the non-metal, e.g. chloride, bromide, duor-ide, etc. Notice that the prefix hydro- is omitted, and that the name of the metal precedes, c.g. sodium chloride, potassium bromide, calcium fluoride, etc. It will soon be shown experimentally that salts may be regarded as derived from... 

Inverted forms of the chemical names (parent index headings) are used for most entries in the alphabetically ordered index. Organic names are listed at the parent based on Rule C-10, Nomenclature of Organic Chemistry, 1979 Edition. Coordination compounds, salts and ions are listed once at each metal or central atom parent index heading. Simple salts and binary compounds are entered in the usual uninverted way, e.g.. Sulfur oxide (SxO), Lira-nium( V) chloride (UCL). 

When atomic theory developed to the point where it was possible to write specific formulae for the various oxides and other binary compounds, names reflecting composition more or less accurately then became common no names reflecting the composition of the oxosalts were ever adopted, however. As the number of inorganic compounds rapidly grew, the essential pattern of nomenclature was little altered until near the end of the 19th century. As a need arose, a name was proposed and nomenclature grew by accretion rather than by systematization. 

Chemical nomenclature deals with names of elements and their combinations. Whereas writing the symbol or the name of an element is straightforward, a choice of which element to write first in the formula and in the name has to be made as soon as an element is associated with one or more other elements to form, for example, a binary compound. The order of citation of elements in formulae and names is based upon the methods outlined below. Furthermore, groups of atoms, such as ions, ligands in coordination compounds and substituent groups in derivatives of parent hydrides, are ordered according to specified rules. 

Since this is the book s first look at nomenclature, we limit ourselves to molecular binary compounds, those made up of only two elements, both nonmetals. Other binary compounds are named in Chapter 4, after you learn more about ions. Let s start by naming four molecular binary compounds to get an idea how names are formed, and then follow this with some rules. 

Many ionic componnds are binary compounds, or compounds formed from just two elements. For binary componnds the first element named is the metal cation, followed by the nonmetallic anion. Thus NaCl is sodium chloride. The anion is named by taking the first part of the element name (chlorine) and adding -ide. Potassium bromide (KBr), zinc iodide (Znl2), and aluminum oxide (AI2O3) are also binary componnds. Table 2.2 shows the -ide nomenclature of some common monatomic anions according to their positions in the periodic table. 

Chemical nomenclature is the systematic naming of compounds based on their formulas or structures. Rules are given for naming ionic compounds, binary molecular compounds, acids, and hydrates. 

Unlike ionic compounds, molecular compounds are composed of individual covalently bonded units, or molecules. Chemists use two nomenclature systems to name binary molecules. The newer system is the Stock system for naming molecular compounds, which requires an understanding of oxidation numbers. This system will be discussed in Section 2. 

In Section 1, we introduced the use of Roman numerals to denote ionic charges in the Stock system of naming ionic compounds. The Stock system is actually based on oxidation numbers, and it can be used as an alternative to the prefix system for naming binary molecular compounds. In the prefix system, for example, SO2 and SO3 are named sulfur dioxide and sulfur trioxide, respectively. Their names according to the Stock system are sulfur(IV) oxide and sulfur(VI) oxide. The international body that governs nomenclature has endorsed the Stock system, which is more practical for complicated compounds. Prefix-based names and Stock-system names are still used interchangeably for many simple compounds, however. 

The name of a BINARY COMPOUND, a compound composed of two elements, is usually derived from the names of the elements (see back cover) usually, the metallic or electropositive element is written first and the second element is given the suffix -ide. There are four systems of nomenclature ... 

Names and Formulas of Inorganic Compounds—In this section on the nomenclature of inorganic compounds, the names and formulas of two-element or binary compounds are considered first. The... 

Ans. The three compounds belong to different nomenclature classes. Aluminum in its compounds always forms 3+ ions, and thus there is no need to state 3+ in the name. Cobalt forms 2+ and 33-ions, and we need to designate which of these exists in this compound. PCI, is a binary nonmctal-nonmetal compound, using a prefix to denote the number of chlorine atoms. 

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