Atomic symbols Hill order

Briefly, notation systems attempt to record full, multidimensional structural descriptions in a linear form, by the use of more comprehensive symbols than atoms and bonds (e.g. symbols for particular chains, rings, functional groups). Thus, more information is recorded implicitly, in Uie rides of the notation, and less is recorded explicitly in the notations for individual compounds. The rules can therefore be quite complicated, in order to ensure the notations are unique and unambiguous. For the Wiswesser Line Notation, the rules are given in Smith, E. G. The Wis-wesser Line-Formula Chemical Notation. New York McGraw-Hill 1968. In this notation, for example, saturated carbon chains are simply indicated by an arable numeral equal to the number of carbons in the chain, branch-... 

The empirical formula is the molecular formula of a chemical compound. The order of atoms follows tlie Hill system which is utilized by the Chemical Abstracts Services and by the Beilstein Institute. Within the empirical formula C is the first element symbol, H is the second, the other element symbols are added in alphabetical order. The empirical formula does not take into account of any crystal water content. Using this field for searches requires that the above guidelines are strictly followed. 

The molecular formula of a compound carries information only about the number of atoms contained in a molecule. For example, the molecular formula C2H 0 describes molecules made of two C atoms, six H atoms, and a single 0 atom. Usually C is listed first, followed by H, if any, and other element symbols in alphabetic order. This is termed the Hill system [128]. 

The molecules are arranged according to the Hill system [OOHil]. This means that the moleeules are arranged in alphabehcal order of the element symbols except caibon atoms which are written first... 

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