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Elementary reaction

 

 
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Elementary reaction
 
 
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An elementary reaction is a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 in which one or more of the chemical species
Chemical species

Chemical species are atoms, molecules, molecular fragments, ions, etc., as entities being subjected to a chemical process or to a measurement. Generally, a chemical species can be defined as an ensemble of chemically identical molecular entity that can explore the same set of molecular energy levels on a characteristic or delineated time scal...
 react directly to form products in a single reaction step
Reaction step

A reaction step of a chemical reaction is defined as: "An elementary reaction, constituting one of the stages of a stepwise reaction in which a reaction intermediate is converted into the next reaction intermediate in the sequence of intermediates between reactants and products"....
 and with a single transition state
Transition state

The transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest energy along this reaction coordinate....
.

In a unimolecular elementary reaction a molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
, A, dissociates
Dissociation (chemistry)

Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller molecules, ions, or Radical , usually in a reversible manner....
 or isomerises
Isomerisation

In chemistry isomerisation is the process by which one molecule is transformed into another molecule which has exactly the same atoms, but the atoms are rearranged e.g....
 to form the products(s). The rate
Reaction rate

The reaction rate or rate of reaction for a reactant or product in a particular chemical reaction is intuitively defined as how fast a reaction takes place....
 of such a reaction, at constant temperature, is proportional to the concentration of the species A In a bimolecular elementary reaction, two atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s, molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
s, ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
s or radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
s, A and B, react together to form the product(s) The rate of such a reaction, at constant temperature, is proportional to the product of the concentrations of the species A and B. This rate expression can be derived from first principles by using collision theory
Collision theory

The Collision theory, proposed by Max Trautz and William Lewis in 1916 and 1918, qualitatively explains how chemical reactions occur and why reaction rates differ for different reactions....
. The rate expression for an elementary bimolecular reaction is sometimes referred to as the Law of Mass Action as it was first proposed by Guldberg and Waage in 1864.






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An elementary reaction is a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 in which one or more of the chemical species
Chemical species

Chemical species are atoms, molecules, molecular fragments, ions, etc., as entities being subjected to a chemical process or to a measurement. Generally, a chemical species can be defined as an ensemble of chemically identical molecular entity that can explore the same set of molecular energy levels on a characteristic or delineated time scal...
 react directly to form products in a single reaction step
Reaction step

A reaction step of a chemical reaction is defined as: "An elementary reaction, constituting one of the stages of a stepwise reaction in which a reaction intermediate is converted into the next reaction intermediate in the sequence of intermediates between reactants and products"....
 and with a single transition state
Transition state

The transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest energy along this reaction coordinate....
.

In a unimolecular elementary reaction a molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
, A, dissociates
Dissociation (chemistry)

Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller molecules, ions, or Radical , usually in a reversible manner....
 or isomerises
Isomerisation

In chemistry isomerisation is the process by which one molecule is transformed into another molecule which has exactly the same atoms, but the atoms are rearranged e.g....
 to form the products(s). The rate
Reaction rate

The reaction rate or rate of reaction for a reactant or product in a particular chemical reaction is intuitively defined as how fast a reaction takes place....
 of such a reaction, at constant temperature, is proportional to the concentration of the species A In a bimolecular elementary reaction, two atom
Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s, molecule
Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
s, ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
s or radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
s, A and B, react together to form the product(s) The rate of such a reaction, at constant temperature, is proportional to the product of the concentrations of the species A and B. This rate expression can be derived from first principles by using collision theory
Collision theory

The Collision theory, proposed by Max Trautz and William Lewis in 1916 and 1918, qualitatively explains how chemical reactions occur and why reaction rates differ for different reactions....
. The rate expression for an elementary bimolecular reaction is sometimes referred to as the Law of Mass Action as it was first proposed by Guldberg and Waage in 1864. An example of this type of reaction is a cycloaddition
Cycloaddition

A cycloaddition is a pericyclic chemical reaction, in which two pi bond are lost and two sigma bond are gained. The resulting reaction is a cyclization reaction....
 reaction.

Three chemical species must react simultaneously with each other in a trimolecular elementary reactions. It follows that such reactions are very rare.

Any chemical reaction can be broken down into a set of elementary reactions. It is not always possible to derive an overall rate equation
Rate equation

The rate law or rate equation for a chemical reaction is an equation which links the reaction rate with concentrations or pressures of reactants and constant parameters ....
 for non-trivial reaction schemes, but analytical solutions are possible in favourable cases, see, for example, the steady state approximation
Steady state (chemistry)

In chemistry, a steady state is a situation in which all thermodynamic variable are constant in spite of ongoing processes that strive to change them....
 or Michaelis-Menten kinetics
Michaelis-Menten kinetics

File:Michaelis-Menten.pngMichaelis?Menten kinetics approximately describes the enzyme kinetics of many enzymes. It is named after Leonor Michaelis and Maud Menten....
 for enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
-based reactions.