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Quantities, Units and Symbols in Physical Chemistry, also known as the Green Book, is a compilation of terms and symbols widely used in the field of physical chemistry. It also includes a table of physical constants , tables listing the properties of elementary particles , chemical elements , and nuclides , and information about conversion ...
Chemical symbols are the abbreviations used in chemistry, mainly for chemical elements; but also for functional groups, chemical compounds, and other entities. Element symbols for chemical elements, also known as atomic symbols , normally consist of one or two letters from the Latin alphabet and are written with the first letter capitalised.
The general rule is to use the name most commonly used to refer to the compound, as evidenced by use in reliable sources (in line with WP:COMMONNAME). Classes of compounds may have more specific guidance on naming, such as the use of international nonproprietary names for pharmaceutical compounds (see WP:NCMED and below ).
The table below shows a comparison of Greek letters rendered in TeX and HTML. The font used in the TeX rendering is an italic style. The font used in the TeX rendering is an italic style. This is in line with the convention that variables should be italicized.
Capital letters "B" and "I" are suffixed, together with atom counts, if chlorine atoms have been replaced with bromine or iodine. If there are two carbons, the isomer without suffix is the most symmetrical; after this, lower-case suffixed letters "a", "b", ..., are added, moving forwards through the alphabet as symmetry decreases.
The 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.
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.
Contrary to the usual English style for parentheses, there is no space between the end of the element name and the opening parenthesis: for AgF, the correct style is "silver(I) fluoride" not "silver (I) fluoride".