Chemical symbol: Difference between revisions
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'''Chemical symbols''' are the international standard way to denote [[chemical elements]]. In particular, they are used in chemical formulas to describe the composition and structure of [[molecule]]s, and in [[reaction formula]]s. | '''Chemical symbols''' are the international standard way to denote [[chemical elements]]. In particular, they are used in chemical formulas to describe the composition and structure of [[molecule]]s, and in [[reaction formula]]s. | ||
A chemical symbol consists of one or two letters | A chemical symbol consists of one or two letters: the initial letter of its scientific name in uppercase which, | ||
in most cases, is followed by a suitable lowercase letter from the name. | in most cases, is followed by a suitable lowercase letter from the name. | ||
(Sometimes, on a temporary basis, for new artificial elements initially 3-letter symbols | (Sometimes, on a temporary basis, for new artificial elements initially 3-letter symbols are used.) | ||
Well-known examples of one-letter symbols are H for [[hydrogen]] and O for [[oxygen]] | Well-known examples of one-letter symbols are H for [[hydrogen]] and O for [[oxygen]]; | ||
Ca is the two-letter symbol for [[calcium]]. | Ca is the two-letter symbol for [[calcium]]. | ||
For most elements the symbol fits its English name because this name is also derived from the scientific name (which usually is of Greek or Latin origin). | For most elements the symbol fits its English name because this name is also derived from the scientific name (which usually is of Greek or Latin origin). | ||
However, in a few cases there is no relation between the English word and its symbol. | However, in a few cases there is no relation between the English word and its symbol. | ||
For instance, Fe (derived from Latin "ferrum") is the symbol for [[iron]]. | For instance, Fe (derived from Latin "ferrum") is the symbol for [[iron]]. | ||
<br> | |||
Element number 112 has the symbol Uub, for its temporary name Ununbium (which is derived from Latin for one-one-two). | |||
For a complete list of all chemical symbols see the alphabetical [[/Catalogs|list]]. | |||
In addition, subscripts and superscripts attached to the basic symbol are used to carry additional information. | |||
== Compounds == | |||
The number of atoms in a [[molecule]] is indicated by a subscript (on the right). | |||
For example, O<sub>2</sub> is oxygen, and O<sub>3</sub> is [[ozone]]. | |||
== Ions == | == Ions == | ||
An [[ion]] of an element is indicated by a superscript, where + and - stand for positive and negative charge, respectively. | |||
An [[ | |||
For example, H<sup>+</sup> means a hydrogen ion, and Ca<sup>2+</sup> a calcium ion (with two electrons missing). | For example, H<sup>+</sup> means a hydrogen ion, and Ca<sup>2+</sup> a calcium ion (with two electrons missing). | ||
<br> | <br> | ||
The ion H<sup>+</sup> of hydrogen is a [[proton]] | The ion H<sup>+</sup> of hydrogen is a [[proton]] | ||
which — in atomic reactions — is also indicated as p. | which—in atomic reactions—is also indicated as p. | ||
(Similarly, a [[neutron]] is indicated by n.) | |||
== Isotopes == | == Isotopes == | ||
In atom physics, [[isotope]]s of an element are distinguished | In atom physics, [[isotope]]s of an element are distinguished | ||
by adding the [[atomic mass]] as a superscript (usually, but not always, attached to the left of the symbol). | by adding the [[atomic mass]] as a superscript (usually, but not always, attached to the left of the symbol). | ||
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The isotopes of hydrogen have symbols of their own: | The isotopes of hydrogen have symbols of their own: | ||
<sup>1</sup>H is hydrogen H, <sup>2</sup>H is [[deuterium]] D, and <sup>3</sup>H is [[tritium]] T. | <sup>1</sup>H is hydrogen H, <sup>2</sup>H is [[deuterium]] D, and <sup>3</sup>H is [[tritium]] T. | ||
For convenience, sometimes the [[atomic number]]—which is already implied by the chemical symbol—is added as a subscript on the left. | |||
== Examples == | == Examples == | ||
A simple example for a chemical reaction formula is | A simple example for a chemical reaction formula is | ||
: | : <math>\rm 2 H_2 + O_2 \to 2 H_2 O </math> | ||
which states that hydrogen and oxygen can react and produce water. | which states that hydrogen and oxygen can react and produce water. | ||
A hydrogen ion and a OH-group combine to water: | |||
: <math>\rm H^+ + OH^- \to H_2 O </math> | |||
In | In an atomic fusion reaction, two deuterium atoms can either combine to a tritium atom and emit a proton: | ||
: <math>\rm {}^2D + {}^2D \to {}^3T + p </math> | |||
or to a helium isotope and emit a neutron: | |||
: <math>\rm {}^2_1D + {}^2_1D \to {}^3_2He + n </math> | |||
Revision as of 05:12, 23 October 2013
Chemical symbols are the international standard way to denote chemical elements. In particular, they are used in chemical formulas to describe the composition and structure of molecules, and in reaction formulas. A chemical symbol consists of one or two letters: the initial letter of its scientific name in uppercase which, in most cases, is followed by a suitable lowercase letter from the name. (Sometimes, on a temporary basis, for new artificial elements initially 3-letter symbols are used.)
Well-known examples of one-letter symbols are H for hydrogen and O for oxygen;
Ca is the two-letter symbol for calcium.
For most elements the symbol fits its English name because this name is also derived from the scientific name (which usually is of Greek or Latin origin).
However, in a few cases there is no relation between the English word and its symbol.
For instance, Fe (derived from Latin "ferrum") is the symbol for iron.
Element number 112 has the symbol Uub, for its temporary name Ununbium (which is derived from Latin for one-one-two).
For a complete list of all chemical symbols see the alphabetical list.
In addition, subscripts and superscripts attached to the basic symbol are used to carry additional information.
Compounds
The number of atoms in a molecule is indicated by a subscript (on the right). For example, O2 is oxygen, and O3 is ozone.
Ions
An ion of an element is indicated by a superscript, where + and - stand for positive and negative charge, respectively.
For example, H+ means a hydrogen ion, and Ca2+ a calcium ion (with two electrons missing).
The ion H+ of hydrogen is a proton
which—in atomic reactions—is also indicated as p.
(Similarly, a neutron is indicated by n.)
Isotopes
In atom physics, isotopes of an element are distinguished
by adding the atomic mass as a superscript (usually, but not always, attached to the left of the symbol).
The isotopes of hydrogen have symbols of their own:
1H is hydrogen H, 2H is deuterium D, and 3H is tritium T.
For convenience, sometimes the atomic number—which is already implied by the chemical symbol—is added as a subscript on the left.
Examples
A simple example for a chemical reaction formula is
which states that hydrogen and oxygen can react and produce water.
A hydrogen ion and a OH-group combine to water:
In an atomic fusion reaction, two deuterium atoms can either combine to a tritium atom and emit a proton:
or to a helium isotope and emit a neutron: