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Oxygen is a chemical element; it has symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is Earth's most abundant element, and after hydrogen and helium, it is the third-most abundant element in the universe. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O
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In thermodynamics, the thermodynamic free energy is one of the state functions of a thermodynamic system. The change in the free energy is the maximum amount of work that the system can perform in a process at constant temperature, and its sign indicates whether the process is thermodynamically favorable or forbidden. Since free energy usually contains potential energy, it is not absolute but depends on the choice of a zero point. Therefore, only relative free energy values, or changes in free energy, are physically meaningful.
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Nitrogen dioxide is a chemical compound with the formula NO2 and is one of several nitrogen oxides. NO2 is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use. At higher temperatures, nitrogen dioxide is a reddish-brown gas. Nitrogen dioxide is a paramagnetic, bent molecule with C2v point group symmetry.
Diborane(6), commonly known as diborane, is the chemical compound with the formula B2H6. It is a toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has attracted wide attention for its electronic structure. Several of its derivatives are useful reagents.
Detonation is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations propagate supersonically through shock waves with speeds in the range of 1 km/sec and differ from deflagrations which have subsonic flame speeds in the range of 1 m/sec. Detonation is an explosion of fuel-air mixture. Compared to deflagration, detonation doesn't need to have an external oxidizer. Oxidizers and fuel mix when deflagration occurs. Detonation is more destructive than deflagrations. In detonation, flame front travels through air-fuel faster than sound, while in deflagrations, flame front travels through air-fuel slower than sound
In chemistry, reactivity is the impulse for which a chemical substance undergoes a chemical reaction, either by itself or with other materials, with an overall release of energy.
Soot is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed fuel particles such as coal, cenospheres, charred wood, and petroleum coke that may become airborne during pyrolysis and that are more properly identified as cokes or char.
In chemistry, a hypervalent molecule is a molecule that contains one or more main group elements apparently bearing more than eight electrons in their valence shells. Phosphorus pentachloride, sulfur hexafluoride, chlorine trifluoride, the chlorite ion, and the triiodide ion are examples of hypervalent molecules.
Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to calculate elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example is an explanation for the color of gold: due to relativistic effects, it is not silvery like most other metals.
Singlet oxygen, systematically named dioxygen(singlet) and dioxidene, is a gaseous inorganic chemical with the formula O=O (also written as 1
[O
2] or 1
O
2), which is in a quantum state where all electrons are spin paired. It is kinetically unstable at ambient temperature, but the rate of decay is slow.
The alpha effect refers to the increased nucleophilicity of an atom due to the presence of an adjacent (alpha) atom with lone pair electrons. This first atom does not necessarily exhibit increased basicity compared with a similar atom without an adjacent electron-donating atom, resulting in a deviation from the classical Brønsted-type reactivity-basicity relationship. In other words, the alpha effect refers to nucleophiles presenting higher nucleophilicity than the predicted value obtained from the Brønsted basicity. The representative examples would be high nucleophilicities of hydroperoxide (HO2−) and hydrazine (N2H4). The effect is now well established with numerous examples and became an important concept in mechanistic chemistry and biochemistry. However, the origin of the effect is still controversial without a clear winner.
Radiation damage is the effect of ionizing radiation on physical objects including non-living structural materials. It can be either detrimental or beneficial for materials.
Physical organic chemistry, a term coined by Louis Hammett in 1940, refers to a discipline of organic chemistry that focuses on the relationship between chemical structures and reactivity, in particular, applying experimental tools of physical chemistry to the study of organic molecules. Specific focal points of study include the rates of organic reactions, the relative chemical stabilities of the starting materials, reactive intermediates, transition states, and products of chemical reactions, and non-covalent aspects of solvation and molecular interactions that influence chemical reactivity. Such studies provide theoretical and practical frameworks to understand how changes in structure in solution or solid-state contexts impact reaction mechanism and rate for each organic reaction of interest.
In chemistry, solvent effects are the influence of a solvent on chemical reactivity or molecular associations. Solvents can have an effect on solubility, stability and reaction rates and choosing the appropriate solvent allows for thermodynamic and kinetic control over a chemical reaction.
References
- ↑ "The 'Chemical Age' Chemical Dictionary. Chemical Terms", Ernest Benn Limited, London, 1924, p.107 (link)
- 1 2 3 Jensen, William B (1990). "Whatever Happened to the Nascent State?" (PDF). Bulletin for the History of Chemistry (5): 26–36. Retrieved 6 May 2017.
- ↑ Zenghelis, Constantine (1920). "Nouvelles recherches sur l'action des gaz extremement divisés". Comptes Rendus. 171: 167–170.
- ↑ Reedy, J. H.; Biggers, E. D. (1 September 1942). "The nascent state". Journal of Chemical Education. 19 (9): 403. Bibcode:1942JChEd..19..403R. doi:10.1021/ed019p403. ISSN 0021-9584.
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