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Screenshot of the CAS Common Chemistry database with information about caffeine ().. A CAS Registry Number [1] (also referred to as CAS RN [2] or informally CAS Number) is a unique identification number, assigned by the Chemical Abstracts Service (CAS) in the US to every chemical substance described in the open scientific literature, in order to index the substance in the CAS Registry.
This is a list of CAS numbers by chemical formulas and chemical compounds, indexed by formula.The CAS number is a unique number applied to a specific chemical by the Chemical Abstracts Service (CAS).This list complements alternative listings to be found at list of inorganic compounds and glossary of chemical formulae
Chemical formula Synonyms CAS number C 20 F 42: perfluoroicosane: 37589-57-4 C 20 H 6 I 4 Na 2 O 5: erythrosine: 16423-68-0 C 20 H 12: perylene: 198-55-0 C 20 H 12: benz(e)acephenanthrylene: 205-99-2 [1] C 20 H 12 O 5: fluorescein: 2321-07-5 C 20 H 13 N 3 O 7: anthracene picric acid: 5937-78-0 C 20 H 14 NO 4: sanguinarine: 2447-54-3 C 20 H 14 O ...
Atom connections (prefix: "c"). The atoms in the chemical formula (except for hydrogens) are numbered in sequence; this sublayer describes which atoms are connected by bonds to which other ones. The type of those bonds is later specified in the stereochemical layer prefixed by "b". Hydrogen atoms (prefix: "h"). Describes how many hydrogen atoms ...
[5] A trick is to count up valence electrons, then count up the number of electrons needed to complete the octet rule (or with hydrogen just 2 electrons), then take the difference of these two numbers. The answer is the number of electrons that make up the bonds. The rest of the electrons just go to fill all the other atoms' octets.
CAS Headquarters Complex, completed in 1965 with addition (on left) in 1973. Columbus, Ohio. Chemical Abstracts (CA) began as a volunteer effort and developed from there. The use of volunteer abstractors was phased out in 1994. Chemical Abstracts has been associated with the American Chemical Society in one way or another since 1907. [13]
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
The ion/molecule/atom surrounding the central ion/molecule/atom is called a ligand. This number is determined somewhat differently for molecules than for crystals. For molecules and polyatomic ions the coordination number of an atom is determined by simply counting the other atoms to which it is bonded (by either single or multiple bonds). [1]