IUPAC prefers the British spellings " aluminium " and " caesium " over the U. S. spellings " aluminum " and " cesium ", and the U. S. " sulfur " over the British " sulphur ".

The term salt is misleading and IUPAC prefers diaryl-λ < sup > 3 </ sup >- iodane.

A more stable isotope (< sup > 231 </ sup > Pa ) of protactinium was discovered in 1917 / 18 by Otto Hahn and Lise Meitner, and they choose the name proto-actinium, but then the IUPAC named it finally protactinium in 1949 and confirmed Hahn and Meitner as discoverers.

In 2011, IUPAC evaluated the 2006 results of the Dubna-Livermore collaboration and concluded: " The three events reported for the Z = 118 isotope have very good internal

In May 2009, the Joint Working Party ( JWP ) of IUPAC published a report on the discovery of copernicium in which they acknowledged the discovery of the isotope < sup > 283 </ sup > Cn.

Prior to 1959 both the IUPAP and IUPAC tended to use oxygen to define the mole, the chemists defining the mole as the number of atoms of oxygen which had mass 16 g, the physicists using a similar definition but with the oxygen-16 isotope only.

It is estimated that it requires around 10 < sup >− 14 </ sup > s for the nucleons to arrange themselves into nuclear shells, at which point the compound nucleus becomes an nuclide, and this number is used by IUPAC as the minimum half-life a claimed isotope must have to potentially be recognised as being discovered.

Therefore primer sequence corresponding to the amino acid isoleucine might be " ATH ", where A stands for adenine, T for thymine, and H for adenine, thymine, or cytosine, according to the genetic code for each codon, using the IUPAC symbols for degenerate bases.

The names and symbols of elements 113, 115, 117, and 118 are provisional until permanent names for the elements are decided on, usually within a year after the discovery acknowledgement by IUPAC.

Thus, for hydrogen chloride, the IUPAC name would be aqueous hydrogen chloride.

In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen ( H ), which is nominally a group 1 element but not normally considered to be an alkali metal as it rarely exhibits behaviour comparable to that of the alkali metals.

More recent IUPAC recommendations now suggest the newer term " hydronium " be used in favor of the older accepted term " oxonium " to illustrate reaction mechanisms such as those defined in the Brønsted – Lowry and solvent system definitions more clearly, with the Arrhenius definition serving as a simple general outline of acid – base character.

There was an element naming controversy as to what the elements from 104 to 106 were to be called ; the IUPAC adopted unnilseptium ( symbol Uns ) as a temporary, systematic element name for this element.

In 1994 a committee of IUPAC recommended that element 107 be named bohrium, not nielsbohrium, since there was no precedence for using a scientist's complete name in the naming of an element.

The IUPAC subsequently decided that bohrium salts should be called bohriates.

Since the definition of the equivalence factor may not be unequivocal, IUPAC and NIST discourage the use of normality.

In 1992 the IUPAC / IUPAP Transfermium Working Group assessed the claims of the two groups and concluded that confidence in the discovery grew from results from both laboratories and the claim of discovery should be shared.

It was argued by IUPAC that the Berkeley laboratory had already been recognized several times in the naming of elements ( i. e., berkelium, californium, americium ) and that the acceptance of the names rutherfordium and seaborgium for elements 104 and 106 should be offset by recognizing the Russian team's contributions to the discovery of elements 104, 105 and 106.

In 1994 a committee of IUPAC recommended that element 108 be named hahnium ( Hn ), in spite of the long-standing convention to give the discoverer the right to suggest a name.

When trying to define rigorously whether an arrangement of atoms is " sufficiently stable " to be considered a molecule, IUPAC suggests that it " must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state ".

General: Symbols for quantities should be chosen according to the international recommendations from ISO 80000, the IUPAP red book and the IUPAC green book.

In 1992, the IUPAC / IUPAP Transfermium Working Group ( TWG ) assessed the claims of discovery and concluded that both teams provided contemporaneous evidence to the synthesis of element 104 and that credit should be shared between the two groups.

In 1994, IUPAC suggested the name dubnium to be used since rutherfordium was suggested for element 106 and IUPAC felt that the Dubna team should be rightly recognized for their contributions.

In 1994 a committee of IUPAC recommended that element 106 be named rutherfordium and adopted a rule that no element can be named after a living person.

In 1971, the International Union of Pure and Applied Chemistry ( IUPAC ) said that for the purposes of specifying the properties of substances, " the standard pressure " should be defined as precisely 100 kPa (≈ 750. 01 torr ) or 29. 53 inHg rather than the 101. 325 kPa value of “ one standard atmosphere ”.

In 1979 the IUPAC published recommendations according to which the element was to be called ununoctium, a systematic element name, as a placeholder until the discovery of the element is confirmed and the IUPAC decides on a name.

According to current guidelines from IUPAC, the ultimate name for all new elements should end in "- ium ", which means the name for ununoctium may end in "- ium ", not "- on ", even if ununoctium turns out to be a noble gas, which traditionally have names ending in "- on " ( with the exception of helium, which was not known to be a noble gas when it was discovered ).

In layman's terms, the stoichiometric coefficient ( or stoichiometric number in the IUPAC nomenclature ) of any given component is the number of molecules which participate in the reaction as written.

Oxalate ( IUPAC: ethanedioate ) is the dianion with the formula C < sub > 2 </ sub > O < sub > 4 </ sub >< sup > 2 −</ sup >, also written ( COO )< sub > 2 </ sub >< sup > 2 −</ sup >.

This notation is now universal and is recommended by the IUPAC.

The latter " concise notation " is used for example by IUPAC in stating the atomic mass of elements.

In modern IUPAC notation, it is called Group 14.

In modern IUPAC notation, it is called Group 15.

Using IUPAC notation in which the brackets contain the natural variables ( other than the main four ), we have:

The PROSITE notation uses the IUPAC one-letter codes and conforms to the above description with the exception that a concatenation symbol,, is used between pattern elements, but it is often dropped between letters of the pattern alphabet.

The IUPAC naming conventions are that annulenes with 7 or more carbon atoms are named as annulene, where n is the number of carbon atoms in their ring, though sometimes the smaller annulenes are referred to using the same notation, and benzene is sometimes referred to simply as annulene.

( Note: When discussing periodic table groups, semiconductor physicists always use an older notation, not the current IUPAC group notation.

The IUPAC preferred notation however, with takes electrons into account and not atoms.

According to IUPAC notation, microporous materials have pore diameters of less than 2 nm and macroporous materials have pore diameters of greater than 50 nm ; the mesoporous category thus lies in the middle.

For purposes of international communication and trade, the official names of the chemical elements both ancient and more recently recognized are decided by the International Union of Pure and Applied Chemistry ( IUPAC ), which has decided on a sort of international English language, drawing on traditional English names even when an element's chemical symbol is based on a Latin or other traditional word, for example adopting " gold " rather than " aurum " as the name for the 79th element ( Au ).

For ordinary communication, to spare a tedious description, the official IUPAC naming recommendations are not always followed in practice, except when it is necessary to give a concise definition to a compound, or when the IUPAC name is simpler ( e. g. ethanol instead of ethyl alcohol ).