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The IUPAC nomenclature of inorganic chemistry is a systematic way of naming inorganic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). Ideally, every inorganic compound should have a name from which an unambiguous formula can be determined. There is also a IUPAC nomenclature of organic chemistry. The names "caffeine" and "3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione" both describe the same chemical. The systematic name encodes the structure and composition of the caffeine molecule in some detail, and provides an unambiguous reference to this compound, whereas the name "caffeine" just names it. These advantages make the systematic name far superior to the common name when absolute clarity and precision is required. However, even professional chemists will use the non-systematic name almost all of the time, because caffeine is a well-known common chemical with a unique structure. Similarly, the chemical water is always known as such, never as "dihydrogen monoxide." Positively charged ions are called cations and negatively charged ions are called anions. The cation is always named first. Ions can be metals or polyatomic ions. Therefore the name of the metal or positive polyatomic ion is followed by the name of the non-metal or negative polyatomic ion. The positive ion retains its element name whereas for a single non-metal anion the ending is changed to -ide. Example: sodium chloride, potassium oxide, or calcium carbonate. When the metal has more than one possible ionic charge or oxidation number the name becomes ambiguous. In these cases the oxidation number of the metal ion is represented by a Roman numeral in parentheses immediately following the metal ion name. For example in uranium(VI) fluoride the oxidation number of uranium is 6. Another example is the iron oxides. FeO is iron(II) oxide and Fe2O3 is iron(III) oxide. An older system used prefixes and suffixes to indicate the oxidation number, according to the following scheme:
Thus the four oxyacids of chlorine are called hypochlorous acid (HOCl), chlorous acid (HOClO), chloric acid (HOClO2) and perchloric acid (HOClO3), and their respective conjugate bases are the hypochlorite, chlorite, chlorate and perchlorate ions. This system has partially fallen out of use, but survives in the common names of many chemical compounds: the modern literature contains few references to "ferric chloride" (instead calling it "iron(III) chloride"), but names like "potassium permanganate" (instead of "potassium manganate(VII)") and "sulfuric acid" abound. Naming simple ionic compounds An ionic compound is named by its cation followed by its anion. See polyatomic ions for a list of possible ions. For cations that take on multiple charges, the charge is written using Roman numerals in parentheses immediately following the element name) For example, Cu(NO3)2 is copper(II) nitrate, because the charge of two nitrate ions is 2 × −1 = −2, and since the net charge of the ionic compound must be zero, the Cu ion has a 2+ charge. This compound is therefore copper(II) nitrate. The Roman numerals in fact show the oxidation number, but in simple ionic compounds (i.e., not metal complexes) this will always equal the ionic charge on the metal. For a simple overview see *, for more details see selected pages from IUPAC rules for naming inorganic compounds. List of common ion names Monatomic anions: Cl− chloride S2− sulfide P3− phosphide Polyatomic ions: NH4+ ammonium H3O+ hydronium NO3− nitrate NO2− nitrite ClO− hypochlorite ClO2− chlorite ClO3− chlorate ClO4− perchlorate SO32− sulfite SO42− sulfate HSO3− hydrogen sulfite (or bisulfite) HCO3− hydrogen carbonate (or bicarbonate) CO32− carbonate PO43− phosphate HPO42− hydrogen phosphate H2PO4− dihydrogen phosphate CrO42− chromate Cr2O72− dichromate BO33− orthoborate AsO43− arsenate C2O42− oxalate CN− cyanide SCN− thiocyanate MnO4− permanganate Naming hydrates Hydrates are ionic compounds that have absorbed water. They are named as the ionic compound followed by a numerical prefix and -hydrate. The numerical prefixes used are listed below: Naming molecular compounds Inorganic molecular compounds are named with a prefix (see list above) before each element. The more electronegative element is written last and with an -ide suffix. For example, CO2 is carbon dioxide, and CCl4 is carbon tetrachloride. There are some exceptions to the rule, however. The prefix mono- is not used with the first element; for example, CO2 is carbon dioxide, not "monocarbon dioxide". Sometimes prefixes are shortened when the ending vowel of the prefix "conflicts" with a starting vowel in the compound. This makes the compound easier to speak; for example, CO is "carbon monoxide" (as opposed to "monooxide"). Naming acids Acids are named by the anion they form when dissolved in water. If an acid forms an anion named ___ide, it is named hydro___ic acid. For example, hydrochloric acid forms a chloride anion. Secondly, anions with an -ate suffix are formed when acids with an -ic suffix are dissolved, e.g. chloric acid; anions with an -ite suffix are formed when acids with an -ous suffix are dissolved in water, e.g. chlorous acid disassociates into chlorite anions. 2005 Revision of IUPACs Nomenclature for Inorganic Compounds With the last revision of the nomenclature, many things changed. Most important is, that there is no absolute right name for one compound anymore. As long as the name describes the compound sufficiently and unambiguously, the name is correct. Old names such as water, carbonyl or cyano are still tolerated. — The "old names" may still have to be understood, but the systematic IUPAC nomenclature is easier to learn (because it is systematic) and always right to use. There are basically two different ways to describe a compound: compositional and substituive nomenclature. Compositional nomenclature This ansatz tries to describe how a molecule is constructed from some kind of core, one might say complex like. The core(s) of the molecule is the sort of atom with the lowest electronegativity EN (e.g. in CO, C is the core with EN=2.5 whereas O has EN=3.5). This element defines the stem name of the compound. If the compound is negatively charged, the name is complimented by a suffix: -ide if there is no other element is present and -ate in any other case. Then the surrounding atoms and groups are described in a ligand manner. The ligand names are determined similarly to the core name. A -o suffix marks them as a ligand group. Identical groups are taken together with a multiplication prefix (i.e. tri-, tetra- or bis-). After the actual naming, designators for charge, radical function, water of crystallization, bridging or multi co-ordinating ligands are indicated. Brackets are set to eliminate ambiguities. Last but not least, the ligand names (if there are different) are brought separately into alphabetical order: multiplication prefices (only!) are ignored. Cations and anions are treated separately (in this order). Exemplification: Substitutive nomenclature This ansatz generalises the organic nomenclature and follows basically the same rules. All elements are given -ane base names and the unsaturated bonds are filled up with hydrogen atoms. E.g. oxidane is a single oxygen atom, the loose ends of which are connected to hydrogen atoms, we also call it water H2O. Dioxidane is a molecule with a chain of two oxygen atoms, with hydrogen atoms at every loose bond, this makes H2O2 or hydrogen peroxide. See also | ||||||||||||||||||||||
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