chemical symbol

Notation of one or two letters derived from the scientific names of the chemical elements (e.g., S for sulfur, Cl for chlorine, Zn for zinc). Some hark back to Latin names: Au (aurum) for gold, Pb (plumbum) for lead. Others are named for people or places (e.g. einsteinium, Es, for Einstein). The present symbols express the system set out by the atomic theory of matter. John Dalton first used symbols to designate single atoms of elements, not indefinite amounts, and Jons Jacob Berzelius gave many of the current names. Chemical formulas of compounds are written as combinations of the elements' symbols, with numbers indicating their atomic proportions, using various conventions for ordering and grouping. Thus, sodium chloride is written as NaCl and sulfuric acid as H₂SO₄.

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See also chemical formula.

A chemical symbol is an abbreviation or shortened version of the name of a chemical element, generally assigned in relation to its Latin name. Natural elements all have symbols of one or two letters; some man-made elements have temporary symbols of three letters.

Chemical symbols are listed in the periodic table and are used as shorthand and in chemical equations, e.g.,

2H₂ + O₂ → 2H₂O

Because chemical symbols are often derived from the Latin or Greek name of the element, they may not bear much similarity to the common English name, e.g., Na for sodium (Latin natrium) and Au for gold (Latin aurum).

In China, each chemical element is assigned an ideograph as its symbol; most of them have been explicitly created for this purpose (see Chinese characters for chemical elements).

Chemical symbols may also be changed to show if one particular isotope of an atom that is specified, as well as to show other attributes such as ionization and oxidation state of a chemical compound.

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 number of atoms of a nucleotide is shown in the right subscript position (e.g., N₂)
• 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 Na⁺)

For complete listings of the chemical elements and their symbols, see:

• List of elements by symbol
• List of elements by name
• List of elements by number
• Periodic table of the elements