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In chemistry, a symbol is a code for a chemical element. It is usually derived from the name of the element, often in Latin.〔This should not be confused with formula. When a number is present at the bottom right corner of the symbol of the element, only then is it said to be a formula, but if the number is not present, it is a symbol.〕 For example, "He" is the symbol for helium (English name, not known in ancient Roman times), "Pb" for lead (''plumbum'' in Latin), "W" for tungsten (''wolfram'' in German, not known in Roman times). Only the first letter is capitalized. Temporary symbols assigned to newly or not-yet synthesized elements use 3-letter symbols based on their atomic numbers. For example, "Uno" was the temporary symbol for hassium which had the temporary name of ''unniloctium'' and "Uuo" is the symbol for ununoctium (temporary name) with the atomic mass 118. Chemical symbols may be modified by the use of prepended superscripts or subscripts to specify a particular isotope of an atom. Additionally, appended superscripts may be used to indicate the ionization or oxidation state of an element. They are widely used in chemistry and they have been officially chosen by the International Union of Pure and Applied Chemistry. There are also some historical symbols that are currently not official any more. Attached subscripts or superscripts specifying a nucleotide or molecule have the following meanings and positions: * The nucleon number (mass number) is shown in the left superscript position (e.g., 14N) * The proton number (atomic number) may be indicated in the left subscript position (e.g., 64Gd) * If necessary, a state of ionization or an excited state may be indicated in the right superscript position (e.g., state of ionization Ca2+). In astronomy, non-ionised atomic hydrogen is often known as "H I", and ionised hydrogen as "H II".〔(The interstellar medium, with definition of HI and HII regions )〕 * The number of atoms of an element in a molecule or chemical compound is shown in the right subscript position (e.g., N2 or Fe2O3) * A radical is indicated by a dot on the right side (e.g., Cl· for a chloride radical) In Chinese, each chemical element has a dedicated character, usually created for the purpose (see Chemical elements in East Asian languages). However, Latin symbols are also used, especially in formulas. A list of current, dated, as well as proposed and historical signs and symbols is included here with its signification. Also given is each element's atomic number, atomic weight or the atomic mass of the most stable isotope, group and period numbers on the periodic table, and etymology of the symbol. ==Symbols== Antimatter atoms are denoted by a bar above the symbol for their matter counterpart, so e.g. H is the symbol for antihydrogen. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Symbol (chemistry)」の詳細全文を読む スポンサード リンク
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