[...]... systems are also in use Some are traditional, and some are very restricted in their application These include acid nomenclature (inorganic, for oxoacids and derivatives), replacement nomenclature (mainly organic, to denote replacement of skeletal atoms in a parent rather than replacement of hydrogen atoms — oxa-aza replacement is one variant), functional class nomenclature (this is again principally organic... as a consensus is reached in the chemical community that these elements have indeed been synthesised, and a trivial name and symbol have been assigned after the prescribed IUPAC procedures have taken place When the elements are suitably arranged in order of their atomic numbers, a Periodic Table is generated There are many variants, and an IUPAC version is shown in Table 2.2 An atomic symbol can have... synperiplanar (sp) synclinal (sc) anticlinal (as) antiperiplanar (ap) or gauche Note that the terms syn and anti alone are no longer used in this context The chlorine atoms may be described as synperiplanar, synclinal, anticlinal or antiperiplanar to each other In inorganic compounds, stereochemical arrangements other than octahedral or tetrahedral are often observed These will be discussed in more detail... (these as a class are called 'cations') they must be accompanied by negative molecules or atoms (anions) to maintain electroneutrality Many elements can give rise to more than one elementary substance These may be substances containing assemblages of the same mono- or poly-atomic unit but arranged differently in the solid state (as with tin), or they may be assemblages of different polyatomic units (as... composed of a central atom to which are coordinated ligands by (to a first approximation) donor—acceptor electronpair bonds The ligands are grouped as formally anionic or formally neutral The anionic ligands are cited first (alphabetical order of first symbols) and the neutral ligands next (also in alphabetical order of first symbols) The whole coordination entity (which may be positive, negative or neutral)... the use of square brackets to indicate an unbranched chain is shown In organic nomenclature generally and in inorganic names, only two classes of enclosing mark are used, ()and [],with the parentheses being the junior set 3.5 SEQUENCE OF CITATION OF SYMBOLS We have already stated that the sequence of atomic symbols in an empirical or molecular formula is arbitrary, but that in the absence of any other... crossing an energy barrier between different potential-energy minima Examples C' HH 2 1 H HH C' synclinal or gauche conformation antiperiplanar conformation The concept of conformational analysis has led to a better understanding of the spatial arrangements of cyclic alkanes and of the chemical reactivity of functionalized derivatives A specific terminology is used Examples 4 chair 3 envelope conformation... trivial, with the exception of the systematic, provisional names and symbols for the elements of atomic number greater than 109 These provisional names will be superseded eventually by trivial names and symbols In any case, they make little impact on general chemical practice The simplest way to represent chemical substances is to use formulae, which are assemblages of chemical symbols Formulae are particularly... are equal and opposite A chiral molecule is not superimposable on its mirror image, whereas an achiral molecule is Chirality is due to the presence in a molecule of a chiral centre, axis or plane Only chiral centres will be dealt with here A chiral centre is an atom binding a set of ligands in a spatial arrangement that is not superimposable on its mirror image, e.g a carbon compound Cabcd, a phosphorus... molecular formula and the same connectivity, but different spatial arrangements There are three classes of stereoisomer: cis—trans isomers, conformational isomers and enantiomers 3.8.1 cis—trans Isomers These are associated with tetrahedral and octahedral spatial distributions of atoms, and with bonds The stereodescriptors cis and trans indicate the spatial distribution with reference to a plane defined . class="bi x0 y0 w1 h1" alt="" Principles of Chemical Nomenclature A GUIDE TO IUPAC RECOMMENDATIONS Principles of Chemical Nomenclature A GUIDE TO IUPAC. 0-86542-685-6 Library of Congress Cataloging-in-publication Data Leigh, G. J. Principles of chemical nomenclature : a guide to IUPAC recommendations / G.J. Leigh, H .A.