Oxidation state: Difference between revisions
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'''Oxidation state''' is a measure of the degree of [[oxidation]] of an [[atom]] in a [[substance]]. It is defined as the [[charge]] an atom might be imagined to have when [[electrons]] are counted according to an agreed-upon set of rules: | '''Oxidation state''' is a measure of the degree of [[oxidation]] of an [[atom]] in a [[substance]]. It is defined as the [[charge]] an atom might be imagined to have when [[electrons]] are counted according to an agreed-upon set of rules: | ||
# | #The oxidation state of a free [[element]] (uncombined element) is zero; | ||
# | #For a simple (monatomic) [[ion]], the oxidation state is equal to the net charge on the ion; | ||
#[[ | #[[Hydrogen]] has an oxidation state of +1 and [[oxygen]] has an oxidation state of -2 when they are present in most [[compounds]]. Exceptions to this are that hydrogen has an oxidation state of -1 in [[hydrides]] of [[active metal]]s, e.g. [[LiH]], and oxygen has an oxidation state of -1 in [[peroxide]]s, e.g. [[Hydrogen Peroxide|H<sub>2</sub>O<sub>2</sub>]]; | ||
# | #The algebraic sum of oxidation states of all atoms in a neutral molecule must be zero, while in ions the algebraic sum of the oxidation states of the constituent atoms must be equal to the charge on the ion. | ||
For example, the | For example, the | ||
oxidation states of sulfur in | oxidation states of sulfur in H<sub>2</sub>S, S<sub>8</sub> (elementary sulfur), SO<sub>2</sub>, SO<sub>3</sub>, and | ||
H<sub>2</sub>SO<sub>4</sub> are, respectively: -2, 0, +4, +6 and +6. The higher the oxidation | |||
state of a given atom, the greater is its degree of oxidation; the lower the | state of a given atom, the greater is its degree of oxidation; the lower the | ||
oxidation state, the greater is its degree of reduction. | oxidation state, the greater is its degree of reduction. | ||
Latest revision as of 12:24, 3 April 2012
Oxidation state is a measure of the degree of oxidation of an atom in a substance. It is defined as the charge an atom might be imagined to have when electrons are counted according to an agreed-upon set of rules:
- The oxidation state of a free element (uncombined element) is zero;
- For a simple (monatomic) ion, the oxidation state is equal to the net charge on the ion;
- Hydrogen has an oxidation state of +1 and oxygen has an oxidation state of -2 when they are present in most compounds. Exceptions to this are that hydrogen has an oxidation state of -1 in hydrides of active metals, e.g. LiH, and oxygen has an oxidation state of -1 in peroxides, e.g. H2O2;
- The algebraic sum of oxidation states of all atoms in a neutral molecule must be zero, while in ions the algebraic sum of the oxidation states of the constituent atoms must be equal to the charge on the ion.
For example, the oxidation states of sulfur in H2S, S8 (elementary sulfur), SO2, SO3, and H2SO4 are, respectively: -2, 0, +4, +6 and +6. The higher the oxidation state of a given atom, the greater is its degree of oxidation; the lower the oxidation state, the greater is its degree of reduction.
This page was originally sourced from: http://www.iupac.org/goldbook/O04365.pdf accessed April 5, 2008