Reactivity refers to the rate at which a chemical substance tends to undergo a chemical reaction in time. In pure compounds, reactivity is regulated by the physical properties of the sample. For instance, grinding a sample to a higher specific surface area increases its reactivity. In impure compounds, the reactivity is also effected by the inclusion of contaminants. In crystalline compounds, the crystalline form can also affect reactivity. However in all cases, reactivity is primarily due to the sub-atomic properties of the compound. Iron rusting - a chemical reaction with a slow reaction rate. ... Water and steam are two different forms of the same chemical substance A chemical substance is a material with a definite chemical composition. ... For other uses, see Chemical reaction (disambiguation). ... Look up chemical compound in Wiktionary, the free dictionary. ... Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...

Causes of reactivity

In general, any time a chemical reaction occurs it is due to the chemical being able to enter a more stable[better] state. Quantum chemistry provides the most in depth and exact understanding of the reason this occurs. Electrons exist in orbitals that are the result of solving the Schrödinger equation for specific situations. For other uses, see Chemical reaction (disambiguation). ... Quantum chemistry is a branch of theoretical chemistry, which applies quantum mechanics and quantum field theory to address issues and problems in chemistry. ... For other uses, see Electron (disambiguation). ... In chemistry, a molecular orbital is a region in which an electron may be found in a molecule. ... For a non-technical introduction to the topic, please see Introduction to quantum mechanics. ...

All things (values of the n and m_l quantum numbers) being equal, the order of stability of electrons in a system from least to greatest is unpaired with no other electrons in similar orbitals, unpaired with all degenerate orbitals half filled and the most stable is a filled set of orbitals. In order to achieve one of these orders of stability, an atom will react with another atom, thereby stabilizing both atoms. For example, a lone hydrogen atom has a single electron in its 1s orbital. It becomes significantly more stable (as much as 100 kilocalories per mole, or 420 kilojoules per mole) when reacting to form H₂. A quantum number is a number used to parametrise certain properties of particles or other systems in quantum mechanics. ... This article is about the chemistry of hydrogen. ... Etymology: French calorie, from Latin calor (heat), from calere (to be warm). ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... The joule (IPA: or ) (symbol: J) is the SI unit of energy. ...

It is for this same reason that carbon will almost always form four bonds. Its ground state valence configuration is 2s² 2p², half filled. However, the activation energy to go from half filled to fully filled p orbitals is so small it is negligible, and as such carbon will form them almost instantaneously, meanwhile the process releases a significant amount of energy (exothermic). This four equal bond configuration is called sp³ hybridization. For other uses, see Carbon (disambiguation). ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... In chemistry, valence, also known as valency or valency number, is a measure of the number of chemical bonds formed by the atoms of a given element. ... The sparks generated by striking steel against a flint provide the activation energy to initiate combustion in this Bunsen burner. ... In thermodynamics, the word exothermic describes a process or reaction that releases energy in the form of heat. ... four sp³ orbitals three sp² orbitals In chemistry, hybridisation or hybridization (see also spelling differences) is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the qualitative description of atomic bonding properties. ...

Chemical kinetics and reactivity

The rate of any given reaction,

Reactants → Products

is governed by the rate law: A rate law is an equation that relates concentrations of reactants to the reaction rate. ...

Rate = k * [A]

where the rate is the change in the molar concentration in one second in the rate-determining step of the reaction (the slowest step), [A] is the product of the molar concentration of all the reactants raised to the correct order, known as the reaction order, and k is the reaction constant, which is constant for one given set of circumstances (generally temperature and pressure) and independent of concentration. The greater the reactivity of a compound the higher the value of k and the higher the rate. For instance, if,

A+B → C+D

Then: Iron rusting - a chemical reaction with a slow reaction rate. ...

Rate = k * [A]ⁿ * [B]^m

where n is the reaction order of A, m is the reaction order of B, n+m is the reaction order of the full reaction, and k is the reaction constant.

See also

• catalysis
• Reactivity series
• Michaelis-Menten equation
• organic chemistry
• chemical kinetics