In chemical nomenclature, theIUPAC nomenclature of inorganic chemistryis asystematicmethod of naminginorganicchemical compounds,as recommended by theInternational Union of Pure and Applied Chemistry(IUPAC). It is published inNomenclature of Inorganic Chemistry(which is informally called the Red Book).[1]Ideally, everyinorganic compoundshould have a name from which an unambiguousformulacan be determined. There is also anIUPAC nomenclature of organic chemistry.
System
editThe names "caffeine"and"3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione"both signify the same chemical compound. 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 "simply names it. These advantages make the systematic name far superior to the common name when absolute clarity and precision are required. However, for the sake of brevity, 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, H2O is most often simply calledwaterin English, though other chemical namesdo exist.
- Single atomanionsare named with an-idesuffix: for example, H−ishydride.
- Compounds with a positiveion(cation): The name of the compound is simply the cation's name (usually the same as the element's), followed by the anion. For example, NaCl issodium chloride,and CaF2iscalcium fluoride.
- Cationsof transition metals able to take multiple charges are labeled withRoman numeralsin parentheses to indicate theircharge.For example, Cu+is copper(I), Cu2+is copper(II). An older, deprecated notation is to append-ousor-icto the root of the Latin name to name ions with a lesser or greater charge. Under this naming convention, Cu+is cuprous and Cu2+is cupric. For naming metal complexes see the page oncomplex (chemistry).
- Oxyanions(polyatomic anions containing oxygen) are named with-iteor-ate,for a lesser or greater quantity of oxygen, respectively. For example,NO−
2is nitrite, whileNO−
3is nitrate. If four oxyanions are possible, the prefixeshypo-andper-are used: hypochlorite is ClO−,perchlorate isClO−
4. - The prefixbi-is adeprecatedway of indicating the presence of a singlehydrogenion, as in "sodium bicarbonate"(NaHCO3). The modern method specifically names thehydrogenatom. Thus, NaHCO3would be pronounced sodium hydrogen carbonate.
Positively charged ions are called cations and negatively charged ions are called anions. The cation is always named first. Ions can be metals, non-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,orcalcium carbonate.
When the metal has more than one possible ionic charge oroxidation numberthe name becomesambiguous.In these cases the oxidation number (the same as the charge) of the metal ion is represented by a Roman numeral in parentheses immediately following the metal ion name. For example, in uranium(VI) fluoride theoxidation numberofuraniumis 6. Another example is the iron oxides. FeO is iron(II) oxide and Fe2O3is iron(III) oxide.
An older system used prefixes and suffixes to indicate the oxidation number, according to the following scheme:
| Oxidation state | Cations and acids | Anions |
|---|---|---|
| Lowest | hypo- -ous | hypo- -ite |
| -ous | -ite | |
| -ic | -ate | |
| per- -ic | per- -ate | |
| Highest | hyper- -ic | hyper- -ate |
Thus the four oxyacids ofchlorineare calledhypochlorous acid(HOCl), chlorous acid(HOClO),chloric acid(HOClO2) andperchloric acid(HOClO3), and their respectiveconjugate basesarehypochlorite,chlorite,chlorateandperchlorateions. This system has partially fallen out of use, but survives in thecommon namesof manychemical 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.
Traditional naming
editSimple ionic compounds
editAn ionic compound is named by its cation followed by its anion. Seepolyatomic ionfor a list of possible ions.
For cations that take on multiple charges, the charge is written usingRoman numeralsin parentheses immediately following the element name. For example, Cu(NO3)2iscopper(II) nitrate,because the charge of twonitrateions (NO−
3) is 2 × −1 = −2, and since the net charge of theionic compoundmust be zero, the Cu ion has a 2+ charge. This compound is therefore copper(II) nitrate. In the case of cations with a +4 oxidation state, the only acceptable format for the Roman numeral 4 is IV and not IIII.
TheRoman numeralsin fact show theoxidation number,but in simple ionic compounds (i.e., notmetal complexes) this will always equal the ionic charge on the metal. For a simple overview see[1]Archived2008-10-16 at theWayback Machine,for more details seeselected pages from IUPAC rules for naming inorganic compoundsArchived2016-03-03 at theWayback Machine.
List of common ion names
editMonatomic anions:
- NH+
4ammonium - H
3O+
hydronium - NO−
3nitrate - NO−
2nitrite - ClO−
hypochlorite - ClO−
2chlorite - ClO−
3chlorate - ClO−
4perchlorate - SO2−
3sulfite - SO2−
4sulfate - S
2O2–
3thiosulfate - HSO−
3hydrogen sulfite(orbisulfite) - HCO−
3hydrogen carbonate(orbicarbonate) - CO2−
3carbonate - PO3−
4phosphate - HPO2−
4hydrogen phosphate - H
2PO−
4dihydrogen phosphate - CrO2−
4chromate - Cr
2O2−
7dichromate - BO3−
3borate - AsO3−
4arsenate - C
2O2−
4oxalate - CN−
cyanide - SCN−
thiocyanate - MnO−
4permanganate
Hydrates
editHydratesare 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 (seeIUPAC numerical multiplier):
For example, CuSO4·5H2O is "copper(II) sulfate pentahydrate".
Molecular compounds
editInorganic molecular compounds are named with a prefix (see list above) before each element. The moreelectronegativeelement is written last and with an-idesuffix. For example, H2O (water) can be calleddihydrogen monoxide.Organic molecules do not follow this rule. In addition, the prefixmono-is not used with the first element; for example, SO2issulfur dioxide,not "monosulfur dioxide". Sometimes prefixes are shortened when the ending vowel of the prefix "conflicts" with a starting vowel in the compound. This makes the name easier to pronounce; for example, CO is "carbon monoxide" (as opposed to "monooxide" ).
Common exceptions
editThe "a" of the penta- prefix is not dropped before a vowel. As the IUPAC Red Book 2005 page 69 states, "The final vowels of multiplicative prefixes should not be elided (although 'monoxide', rather than 'monooxide', is an allowed exception because of general usage)."
There are a number of exceptions and special cases that violate the above rules. Sometimes the prefix is left off the initial atom: I2O5is known asiodine pentaoxide,but it should be calleddiiodine pentaoxide.N2O3is callednitrogen sesquioxide(sesqui-means1+1⁄2).
The main oxide of phosphorus is calledphosphorus pentaoxide.It should actually bediphosphorus pentaoxide,but it is assumed that there are two phosphorus atoms (P2O5), as they are needed in order to balance the oxidation numbers of the five oxygen atoms. However, people have known for years that the real form of the molecule is P4O10,not P2O5,yet it is not normally calledtetraphosphorus decaoxide.
In writing formulas,ammoniais NH3even though nitrogen is more electronegative (in line with the convention used by IUPAC as detailed in Table VI of the red book). Likewise,methaneis written as CH4even though carbon is more electronegative (Hill system).
Nomenclature of Inorganic Chemistry
edit
Nomenclature of Inorganic Chemistry,commonly referred to by chemists as theRed Book,is a collection of recommendations on IUPAC nomenclature, published at irregular intervals by the IUPAC. The last full edition was published in 2005,[2]in both paper and electronic versions.
| Release year | Title | Publisher | ISBN |
|---|---|---|---|
| 2005 | Recommendations 2005 (Red Book) | RSC Publishing | 0-85404-438-8 |
| 2001 | Recommendations 2000 (Red Book II) (supplement) |
RSC Publishing | 0-85404-487-6 |
| 1990 | Recommendations 1990 (Red Book I) | Blackwell | 0-632-02494-1 |
| 1971 | Definitive Rules 1970 | Butterworth | 0-408-70168-4 |
| 1959 | 1957 Rules | Butterworth | |
| 1940/1941 | 1940 Rules | Scientific journals |
See also
edit- IUPAC nomenclature
- IUPAC nomenclature of organic chemistry
- List of inorganic compounds
- Water of crystallization
- IUPAC nomenclature of inorganic chemistry 2005(theRed Book)
- Nomenclature of Organic Chemistry(theBlue Book)
- Quantities, Units and Symbols in Physical Chemistry(theGreen Book)
- Compendium of Chemical Terminology(theGold Book)
- Compendium of Analytical Nomenclature(theOrange Book)
References
edit- ^Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005- Full text (PDF)
2004 version with separate chapters as pdf:IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004)Archived2008-02-19 at theWayback Machine - ^International Union of Pure and Applied Chemistry(2005).Nomenclature of Inorganic Chemistry(IUPAC Recommendations 2005). Cambridge (UK):RSC–IUPAC.ISBN0-85404-438-8.Electronic version.