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IUPAC nomenclature of inorganic chemistry

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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."

  1. Single atom anions are named with an -ide suffix: for example, H− is hydride.
  2. Compounds with a positive ion (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 is sodium chloride, and CaF2 is calcium fluoride.
  3. Cations able to take on more than one positive charge are labeled with Roman numerals in parentheses. For example, Cu+ is copper(I), Cu2+ is copper(II). An older, deprecated notation is to append -ous or -ic to 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 on complex (chemistry).
  4. Oxyanions (polyatomic anions containing oxygen) are named with -ite or -ate, for a lesser or greater quantity of oxygen. For example, NO2− is nitrite, while NO3− is nitrate. If four oxyanions are possible, the prefixes hypo- and per- are used: hypochlorite is ClO−, perchlorate is ClO4−,
  5. The prefix bi- is a deprecated way of indicating the presence of a single hydrogen ion, as in "sodium bicarbonate" (NaHCO3). The modern method specifically names the hydrogen atom. Thus, NaHCO3 would 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 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:

Oxidation state Cations and acids Anions
Lowest hypo- -ous hypo- -ite
  -ous -ite
  -ic -ate
Highest per- -ic per- -ate

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.

Contents

[edit] Traditional Naming

[edit] 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 [1], for more details see selected pages from IUPAC rules for naming inorganic compounds.

[edit] 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

[edit] 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:

  1. mono-
  2. di-
  3. tri-
  4. tetra-
  5. penta-
  6. hexa-
  7. hepta-
  8. octa-
  9. nona-
  10. deca-

For example, CuSO4 · 5H2O is "copper(II) sulfate pentahydrate".

[edit] 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").

[edit] 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.

[edit] 2005 Revision of IUPAC's 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.

[edit] 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:

compound core ligand(s) functional markers name
H2O dihydrogen oxido μ μ-oxido dihydrogen
ClO3– chlorate oxido (1-) trioxido chlorate(1-)
ClO2– chlorate oxido (1-) dioxido chlorate(1-)
NO• nitrogen oxido (•) oxido nitrogen(•)
ONOO– nitrate dioxido / oxido (1-) (dioxido)oxido nitrate(1-)
K4[Fe(CN)6] potassium / ferrate hexacyanido (4-) potassium hexacyanidoferrate(4-)
K[AuS(S2)] potassium / aurate disulfido / sulfido (1-) potassium (disulfido)sulfido aurate(1-)
[Ni(CO)4] niccol oxidocarbon - tetra(oxidocarbon) niccol
CuSO4•5H2O copper / sulfate oxido water(1/5) copper tetraoxidosulfate—water(1/5)

[edit] 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.

BH3 borane CH4 methane NH3 azane H2O oxidane HF fluorane
AlH3 alumane SiH4 silane PH3 phosphane H2S sulfane HCl chlorane
GaH3 gallane GeH4 germane AsH3 arsane H2Se selane HBr bromane
InH3 indigane SnH4 stannane SbH3 stibane H2Te tellane HI iodane
TlH3 thallane PbH4 plumbane BiH3 bismuthane H2Po polane HAt astatane

[edit] See also

[edit] References

  1. ↑  Nomenclature of Inorganic Chemistry, Recommendations 1990, Oxford:Blackwell Scientific Publications. (1990)

[edit] External links

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