Chemical symbol
Encyclopedia
A chemical symbol is a 1- or 2-letter internationally agreed code for a chemical element
, usually derived from the name of the element, often in Latin
. Only the first letter is capitalised. 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). 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.
Chemical symbols may be modified by the use of superscripts or subscripts
to specify a particular isotope
of an atom. Additionally, superscripts may be used to indicate the ionization
or oxidation state
of an element.
Attached subscripts or superscripts specifying a nucleotide or molecule have the following meanings and positions:
In Chinese
each chemical element has an ideograph
, usually created for the purpose, as its symbol (see Chinese characters for chemical elements
).
For complete listings of the chemical elements and their symbols, see:
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
, usually derived from the name of the element, often in Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
. Only the first letter is capitalised. For example, "He" is the symbol for helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
(English name, not known in ancient Roman times), "Pb" for lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
(plumbum in Latin), "W" for tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
(wolfram in German, not known in Roman times). Temporary symbols
Systematic element name
A systematic element name is the temporary name and symbol assigned to newly synthesized and not yet synthesized chemical elements. In chemistry, a transuranic element receives a permanent name and symbol only after its synthesis has been confirmed. In some cases, this has been a protracted and...
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
Hassium
Hassium is a synthetic element with the symbol Hs and atomic number 108. It is the heaviest member of the group 8 elements. The element was first observed in 1984...
which had the temporary name of Unniloctium.
Chemical symbols may be modified by the use of superscripts or subscripts
Subscript and superscript
A subscript or superscript is a number, figure, symbol, or indicator that appears smaller than the normal line of type and is set slightly below or above it – subscripts appear at or below the baseline, while superscripts are above...
to specify a particular isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of an atom. Additionally, superscripts may be used to indicate the ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
or oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
of an element.
Attached subscripts or superscripts specifying a nucleotide or molecule have the following meanings and positions:
- The nucleonNucleonIn physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...
number (mass numberMass numberThe mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...
) is shown in the left superscript position (e.g., 14N) - The proton number (atomic numberAtomic numberIn chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
) may be indicated in the left subscript position (e.g., 64Gd) - If necessary, a state of ionizationIonizationIonization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
or an excited stateExcited stateExcitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
may be indicated in the right superscript position (e.g., state of ionization Ca2+). In astronomyAstronomyAstronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
, non-ionised atomic hydrogen is often known as "HI", and ionised hydrogen as "HII". - The number of atoms of an element in a moleculeMoleculeA molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
or chemical compoundChemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
is shown in the right subscript position (e.g., N2 or Fe2O3) - A radicalRadical (chemistry)Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...
is indicated by a dot on the right side (e.g., Cl· for a chloride radical)
In Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
each chemical element has an ideograph
Chinese character
Chinese characters are logograms used in the writing of Chinese and Japanese , less frequently Korean , formerly Vietnamese , or other languages...
, usually created for the purpose, as its symbol (see Chinese characters for chemical elements
Chinese characters for chemical elements
The names for chemical elements in East Asian languages, along with those for some chemical compounds , are among the newest words to enter the local vocabularies...
).
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