Allotropes oxygen

An interesting way to bypass the electronic noncomplementarity of typical reactions between transition metal ions or complexes and dioxygen is based on an oxygen atom transfer from an oxygen allotrope, ozone. This approach was very successful in generating aqueous ferryl, an otherwise hardly accessible species71 ... 

We saw in Figure 11.4 that as O2 is consumed, the rate of combustion decreases. The rate of a chemical reaction depends on a number of factors. One of these factors, the concentration of the reacting species, can help us understand why there is an ozone layer in the upper atmosphere, despite the fact that O2 is the more stable of the two oxygen allotropes. To approach this issue for the stratosphere, let s first investigate how reaction rates measured in a laboratory depend on concentration. 

However, around 1965 I was given the task of helping a scientist from the United States to develop a numerical model of the oxygen allotrope distribution in the stratosphere, mesosphere, and lower thermosphere. This project got me highly interested in the photochemistry of atmospheric ozone, and I started an intensive study of the scientific literature. This convinced me of the limited status of scientific knowledge on stratospheric chemistry, thus setting the initial conditions for my scientific career. Instead of the initially proposed Ph.D. research project, I preferred... 

White phosphorus is very reactive. It has an appreciable vapour pressure at room temperature and inflames in dry air at about 320 K or at even lower temperatures if finely divided. In air at room temperature it emits a faint green light called phosphorescence the reaction occurring is a complex oxidation process, but this happens only at certain partial pressures of oxygen. It is necessary, therefore, to store white phosphorus under water, unlike the less reactive red and black allotropes which do not react with air at room temperature. Both red and black phosphorus burn to form oxides when heated in air, the red form igniting at temperatures exceeding 600 K,... 

Oxygen, sulphur and selenium are known to exist in more than one allotropic form. 

This exists in two allotropic forms, oxygen, O2 and ozone, O3. 

Ozone. Ozone is an allotropic form of oxygen, O. Because it is an unstable gas, it must be generated at the point of use. Ozone is an effective, clean oxidizing agent possessing powerful antibacterial and antiviral properties. 

Over 100 years ago it had been demonstrated that ozone (Oj). the unstable triatomic allotrope of oxygen, could destroy molds and bacteria and by 1892 several experimental ozone plants were in operation in Europe. In the 1920s, however, as a result of wartime research, during World War I, chlorine became readily... 

Ozone, O3, is the triatomic allotrope of oxygen. It is an unstable, blue diamagnetic gas with a characteristic pungent odour indeed, it was first detected by means of its smell, as reflected by its name (Greek o eiv, ozein, to smell) coined by C. F. Schonbein in 1840. Ozone can be detected by its smell in concentrations as low as 0.01 ppm the maximum permissible concentration for continuous exposure is 0.1 ppm but levels as high as 1 ppm are considered non-toxic if breathed for less than 10 min. 

Allotropy is a very common phenomenon shown by metals, metalloids, and nonmetals. In the gaseous or liquid state, allotropes most often differ from one another in molecular formula. Consider, for example, the two allotropes of gaseous oxygen, 02, and ozone, 03. 

Allotrope One of two or more forms of an element in the same physical state. Graphite and diamond are allotropes of carbon 02 and 03 are allotropes of oxygen, 250... 

An allotrope of oxygen, ozone, 03 (8), is formed in the stratosphere by the effect of solar radiation on 02 molecules. Its total abundance in the atmosphere is equivalent to a layer that, at the ordinary conditions of 25°C and 1 bar, would cover the Earth to a thickness of only 3 mm, yet its presence in the stratosphere is vital to the maintenance of life on Earth (see Box 13.3). Ozone can be made in the laboratory by passing an electric discharge through oxygen. It is a blue gas that... 

Basic physical properties of sulfur, selenium, and tellurium are indicated in Table 1.3. Downward the sulfur sub-group, the metallic character increases from sulfur to polonium, so that whereas there exist various non-metallic allotropic states of elementary sulfur, only one allotropic form of selenium is (semi)metallic, and the (semi)metallic form of tellurium is the most common for this element. Polonium is a typical metal. Physically, this trend is reflected in the electrical properties of the elements oxygen and sulfur are insulators, selenium and tellurium behave as semiconductors, and polonium is a typical metallic conductor. The temperature coefficient of resistivity for S, Se, and Te is negative, which is usually considered... 

A number of chemical elements, mainly oxygen and carbon but also others, such as tin, phosphorus, and sulfur, occur naturally in more than one form. The various forms differ from one another in their physical properties and also, less frequently, in some of their chemical properties. The characteristic of some elements to exist in two or more modifications is known as allotropy, and the different modifications of each element are known as its allotropes. The phenomenon of allotropy is generally attributed to dissimilarities in the way the component atoms bond to each other in each allotrope either variation in the number of atoms bonded to form a molecule, as in the allotropes oxygen and ozone, or to differences in the crystal structure of solids such as graphite and diamond, the allotropes of carbon. 

Many elements including sulphur, carbon and oxygen can exist in two or more forms with different physical, and often chemical, properties such elements are said to exhibit allotropy and the different forms are known as allotropes or allotropic forms. 

An allotropic form of oxygen (03) (see Allotropy) of considerably greater degradative effect on rubber than oxygen itself. The ozone content of the atmosphere normally varies from 0.5 to 5.0 parts per 100 million (pphm) of air, but in certain areas (notably Los Angeles, USA) it may reach as much as 40 pphm of air. 

This exists in two allotropic forms, oxygen, 02 and ozone, O v Oxygen is a colourless gas which condenses to a pale blue liquid, b.p. 90 K, which is markedly paramagnetic indicating the presence of unpaired electrons (p. 229). Simple valence bond theory (as used in this book) would indicate the structure... 

Carbon is unique among chemical elements since it exists in different forms and microtextures transforming it into a very attractive material that is widely used in a broad range of electrochemical applications. Carbon exists in various allotropic forms due to its valency, with the most well-known being carbon black, diamond, fullerenes, graphene and carbon nanotubes. This review is divided into four sections. In the first two sections the structure, electronic and electrochemical properties of carbon are presented along with their applications. The last two sections deal with the use of carbon in polymer electrolyte fuel cells (PEFCs) as catalyst support and oxygen reduction reaction (ORR) electrocatalyst. 

What the alchemist had isolated from his urine was white phosphorus, one of two common forms, allotropes, of the element. White phosphorus is a waxy solid that is very poisonous and very reactive. As our alchemist observed, when it is exposed to air, a sonrce of oxygen, it bursts into flames. White phosphorus is usually stored under water, protecting it from contact with atmospheric oxygen. 

Allotrope An allotrope is formed when an element or compound exists in more than one form. Carbon is an example of an element found in different forms (e.g., carbon black, graphite, and diamonds). Oxygen has three alio tropes monoatomic or nascent oxygen (O) diatomic oxygen (O ), the gas we breathe and triatomic oxygen (O ), which is known as ozone. 

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