Search Results

Structural Chemistry of Alkali and Alkaline-Earth Metals

Wai-Kee Li, Gong-Du Zhou, and Thomas Chung Wai Mak

in Advanced Structural Inorganic Chemistry

This chapter covers the structural chemistry of Groups 1 and 2 elements, except hydrogen. For Group 1 metals, special attention is paid to the oxides, lithium nitride, inorganic alkali metal ... More

This chapter covers the structural chemistry of Groups 1 and 2 elements, except hydrogen. For Group 1 metals, special attention is paid to the oxides, lithium nitride, inorganic alkali metal complexes, methyllithium compounds, π-complexes of lithium, sodium and potassium, alkalides and electrides, etc. For the Group 2 metals, the coverage includes their complexes, nitrides, low-valent oxides and nitrides, polymeric chains, Grignard reagents, metallocenes, etc. The chapter concludes with a section on the alkali and alkaline-earth metal complexes with inverse crown structures.Less

Past and Present Management of Alfalfa Bees

Theresa L. Pitts-Singer

in Bee Pollination in Agricultural Ecosystems

There is a long history of the use of alfalfa by humans, including the intentional introduction of this forage crop from Eurasia to other continents. For producing alfalfa seeds, the management ... More

There is a long history of the use of alfalfa by humans, including the intentional introduction of this forage crop from Eurasia to other continents. For producing alfalfa seeds, the management systems for two bee pollinators have been developed. Use of managed alkali bees, Nomia melanderi, and alfalfa leafcutting bees, Megachile rotundata, has made alfalfa seed production a viable industry. The management systems for both bee species require care and commitment for combating parasites, pests, and diseases, and for meeting proper environmental conditions. Although the emphasis on the use of alkali bees has diminished, the use of the alfalfa leafcutting bees remains popular. Concerns and new ideas surrounding the current and future use of these bee species as commercial pollinators are discussed.Less

Other heteronuclear diatomic molecules: polar covalent bonds

Arne Haaland

in Molecules and Models: The molecular structures of main group element compounds

This chapter describes the structures of 25 heteronuclear, singly bonded diatomic molecules formed by combination of hydrogen, halogen, or alkali metal atoms (HX, HM, XX', or MM') in terms of their ... More

This chapter describes the structures of 25 heteronuclear, singly bonded diatomic molecules formed by combination of hydrogen, halogen, or alkali metal atoms (HX, HM, XX', or MM') in terms of their electric dipole moments, ionic characters, dissociation energies, and bond distances. The ionic characters of these compounds, as well as those of the alkali metal halides discussed in Chapter 5, increase with increasing difference between the electronegativity coefficients of the two bonded atoms:¦χA - χB¦. Similarly, the dissociation energies are found to increase and the bond distances to decrease with increasing electronegativity differences. A simple formula, the modified Schomaker-Stevenson (MSS) rule, allows the calculation of single bond distances between 17 elements (H and 16 elements in Groups 16-19) with an average error of 2 pm.Less

Experimental studies of momentum density in metals and alloys

N. Shiotani

in X-Ray Compton Scattering

This chapter provides a full review and evaluation of work on: alkali metals and their alloys; beryllium, aluminium and its alloys, silicon, 3d transition metals, their alloys and compounds, and ... More

This chapter provides a full review and evaluation of work on: alkali metals and their alloys; beryllium, aluminium and its alloys, silicon, 3d transition metals, their alloys and compounds, and doped fullerines. Particular attention is given to extent to which Compton data can be used to locate and reconstruct the Fermi surface, and determine the size of Fermi surface break in correlated electron systems. The results are compared to theoretical models and to analogous results from positron annihilation studies of angular correlation radiation.Less

Gaseous alkali metal halides: ionic bonds

Arne Haaland

in Molecules and Models: The molecular structures of main group element compounds

The evaporation of an alkali metal halide (MX) yields a mixture of monomers and smaller amounts of dimers, trimers, and tetramers. This chapter describes the monomers in terms of their electric ... More

The evaporation of an alkali metal halide (MX) yields a mixture of monomers and smaller amounts of dimers, trimers, and tetramers. This chapter describes the monomers in terms of their electric dipole moments, dissociation energies, and bond distances. The spherical ion model is used to construct potential energy curves and to calculate dissociation energies in reasonable agreement with their experimental counterparts from the experimental bond distances. Similar calculations on the dimers and on crystals with rock salt structure indicate that the M-X bond distances should be 5% and 15%, respectively, longer than in the monomers. The polarizable ion model leads to significantly better agreement between experimental and calculated electric dipole moments than the spherical ion model. Finally, the crystal structures of compounds containing a negatively charge alkali metal atom or even an isolated electron as cations are described.Less

TRANSPORT PROPERTIES OF DIFFERENT IONS

A.F. Borghesani

in Ions and electrons in liquid helium

This chapter describes the study of transport properties of several different positive ions in superfluid helium. In addition to alkali and alkaline-earth ions, the still unsolved problem of the ... More

This chapter describes the study of transport properties of several different positive ions in superfluid helium. In addition to alkali and alkaline-earth ions, the still unsolved problem of the so-called exotic ions is considered, which contain negative ions which are faster than the common electron bubbles, whose nature remains unknown. Several hypotheses have been made to explain their nature, among which the most intriguing is the electrino hypothesis, i.e., the possibility that the electron in the electron bubble may undergo fission.Less

Catalysing Chemical Correspondence: James Watt and the Case of Joseph Black and James Keir

Kristen M. Schranz

in James Watt (1736-1819): Culture, Innovation and Enlightenment

James Watt has already been established as a competent eighteenth-century chemist. His role as a chemical correspondent, however, has not been examined adequately. This chapter argues that through ... More

James Watt has already been established as a competent eighteenth-century chemist. His role as a chemical correspondent, however, has not been examined adequately. This chapter argues that through well-timed letters Watt circulated vital knowledge between two contemporary chemists, Joseph Black and James Keir. Two case studies in industrial chemistry—the production of alkali and the separation of plated metals—reveal Watt to be an active letter writer who initiated collaboration between business partners and communicated processes promptly. No mere passive conduit of information, Watt was a confidant who encouraged propriety in the manner of correspondence. He was a lynchpin between Black and Keir when the former was fearful of writing the latter, and he censured ill-timed disclosure of industrial secrets. This chapter concludes that future study of Watt’s epistolary exchanges with other chemists will establish more firmly his mediating role in chemical correspondence in the eighteenth-century Republic of Letters.Less

Resemioticization of Periodicity: A Social Semiotic Perspective

Yu Liu

in Mendeleev to Oganesson: A Multidisciplinary Perspective on the Periodic Table

Chemical periodicity is arguably one of the most important ideas in science, and it has profoundly influenced the development of both modern chemistry and physics ... More

Chemical periodicity is arguably one of the most important ideas in science, and it has profoundly influenced the development of both modern chemistry and physics (Scerri 1997, 229). While the definition of periodicity has remained largely stable in the past 150 years, the periodic system has been visualized in a wide range of forms including (to name just a few) tables, spirals, and zigzags. Furthermore, information technology makes it much easier, and offers innovative ways, to produce new versions of periodic depictions (e.g., WebElements (Winter 1993)). The multitude of periodic visualizations arouses growing interest among scholars with different academic backgrounds. For instance, educational researchers and practitioners (e.g., Waldrip et al. 2010) wrestle with the question of which visual representation will most effectively help students master the subject content of periodicity. Likewise, philosophers tend to identify the ultimate display of the periodic system, which they use as evidence to support a realistic view of periodicity (Scerri 2007, 21). Other researchers, however, take a different attitude toward the stunning diversity of periodic depictions. In a seminal paper, Marchese (2013) examines the visualization of periodicity at different stages of history from the perspectives of tabular, cartographic, and hypermedia design. His analysis illuminates the periodic table’s plasticity and endeavors to justify the constant transformation of the periodic displays as a necessary means to meet scientists’ changing needs. While all these studies generally emphasize the importance of periodic depictions in scientific research and education, they tend to give primacy to the notion of “periodic system.” By contrast, the periodic table seems to play a secondary role, which either passively reflects the chemical law or responds to the evolving knowledge of chemical elements. Such a view runs the risk of underestimating the significant function of the periodic table as a productive research tool, one which enabled Mendeleev to successfully predict the existence and the properties of undiscovered elements such as germanium in 1869 (Kibler 2007, 222). It is important to note that science and technology are “both material and semiotic practices” (Halliday 1998, 228, italics in original). Less

Hypotheses and analogy

Peter R. Anstey

in John Locke and Natural Philosophy

This chapter argues that Locke believed hypotheses and analogical reasoning play a minor role in natural philosophical method and that this view is consistent with that of the proponents of the ... More

This chapter argues that Locke believed hypotheses and analogical reasoning play a minor role in natural philosophical method and that this view is consistent with that of the proponents of the Experimental Philosophy. This is illustrated by his discussions of the acid and alkali theory of matter and by his correspondence with Thomas Molyneux.Less

Environmental Justice: The Mercury Connection

Jerome Nriagu, Niladri Basu, and Simone Charles

in Mercury in the Environment: Pattern and Process

For many communities, exposure to mercury through fish consumption is an exemplary case of environmental injustice. Groups that rely on fishing for food, cultural identity, spiritual wellbeing, or ... More

For many communities, exposure to mercury through fish consumption is an exemplary case of environmental injustice. Groups that rely on fishing for food, cultural identity, spiritual wellbeing, or economic prosperity are more vulnerable to mercury pollution. The vulnerability is heightened because sources and hotspots of mercury are found disproportionately in areas near communities of color, low-income and immigrant communities, and indigenous peoples. This chapter reviews cases where mercury has impacted the health, culture, and identity of local communities. Such communities are victims of environmental injustice because they have derived little or no benefit from the products and services of mercury-releasing industries, but they now bear the burden of the wastes left behind. Existing strategies for reducing mercury exposure are not always effective in communities at risk. Fish advisories that warn of health risks from eating contaminated fish themselves perpetuate environmental injustice. The shift in policy from risk reduction to risk avoidance places these communities in a lose-lose situation: either eat fish and suffer the health effects from contaminants or do not eat fish and suffer the health and cultural effects of losing a critical diet food. By allowing significant mercury contamination to remain in place while advising the population at risk to change their lifestyle, regulators are indirectly perpetuating discrimination against communities that attach different normative values to fish.Less

Melting Ice Rivers

Cheryl Colopy

in Dirty, Sacred Rivers: Confronting South Asia's Water Crisis

From a remote outpost of global warming, a summons crackles over a two-way radio several times a week: . . . Kathmandu, Tsho Rolpa! Babar Mahal, Tsho Rolpa! Kathmandu, ... More

From a remote outpost of global warming, a summons crackles over a two-way radio several times a week: . . . Kathmandu, Tsho Rolpa! Babar Mahal, Tsho Rolpa! Kathmandu, Tsho Rolpa! Babar Mahal, Tsho Rolpa! . . . In a little brick building on the lip of a frigid gray lake fifteen thousand feet above sea level, Ram Bahadur Khadka tries to rouse someone at Nepal’s Department of Hydrology and Meteorology in the Babar Mahal district of Kathmandu far below. When he finally succeeds and a voice crackles back to him, he reads off a series of measurements: lake levels, amounts of precipitation. A father and a farmer, Ram Bahadur is up here at this frigid outpost because the world is getting warmer. He and two colleagues rotate duty; usually two of them live here at any given time, in unkempt bachelor quarters near the roof of the world. Mount Everest is three valleys to the east, only about twenty miles as the crow flies. The Tibetan plateau is just over the mountains to the north. The men stay for four months at a stretch before walking down several days to reach a road and board a bus to go home and visit their families. For the past six years each has received five thousand rupees per month from the government—about $70—for his labors. The cold, murky lake some fifty yards away from the post used to be solid ice. Called Tsho Rolpa, it’s at the bottom of the Trakarding Glacier on the border between Tibet and Nepal. The Trakarding has been receding since at least 1960, leaving the lake at its foot. It’s retreating about 200 feet each year. Tsho Rolpa was once just a pond atop the glacier. Now it’s half a kilometer wide and three and a half kilometers long; upward of a hundred million cubic meters of icy water are trapped behind a heap of rock the glacier deposited as it flowed down and then retreated. The Netherlands helped Nepal carve out a trench through that heap of rock to allow some of the lake’s water to drain into the Rolwaling River. Less

Mojave Desert Scrub Vegetation

Todd Keeler-Wolf

in Terrestrial Vegetation of California, 3rd Edition

Mojave Desert scrub vegetation includes all the shrub and woodland vegetation of the Mojave Desert Region below the cool desert zone. This chapter reviews the classification of Mojave Desert scrub ... More

Mojave Desert scrub vegetation includes all the shrub and woodland vegetation of the Mojave Desert Region below the cool desert zone. This chapter reviews the classification of Mojave Desert scrub vegetation, identifying environmental relationships among and between these types. These vegetation types include alkali sink vegetation, mesquite vegetation, desert riparian vegetation, saltbrush scrub, alkaline marshes, sand dunes, bajadas, hills, and washes.Less

Colorado Desert Vegetation

Allan A. Schoenherr and Jack H. Burk

in Terrestrial Vegetation of California, 3rd Edition

The Colorado Desert of California represents the northwesternmost portion of the Sonoran Desert, which extends into Arizona, Baja California, and Sonora. This chapter describes the types of ... More

The Colorado Desert of California represents the northwesternmost portion of the Sonoran Desert, which extends into Arizona, Baja California, and Sonora. This chapter describes the types of vegetation and distribution of dominant plants in the Colorado Desert, presenting vegetation types based on dominant species and on assemblages of species with similar strategies for coping with specific microclimates and soil types. The plant community types of the Colorado Desert include the creosote bush scrub, cactus scrub, saltbush scrub, alkali sink, microphyll woodland, palm oasis, and psammophytic scrub.Less

Give and Take: Neutralization

Peter Atkins

in Title Pages

The almost infinite can spring from the almost infinitesimal. Two almost infinitesimally small fundamental particles are of considerable interest to ... More

The almost infinite can spring from the almost infinitesimal. Two almost infinitesimally small fundamental particles are of considerable interest to chemists: the proton and the electron. As to the almost infinite that springs from them, almost the whole of the processes that constitute what we call ‘life’ can be traced to the transfer of one or other of these particles from one molecule to another in a giant network of reactions going on inside our cells. I think it quite remarkable, and rather wonderful, that a hugely complex network of extremely simple processes in which protons and electrons hop from one molecule to another, sometimes dragging groups of atoms with them, sometimes not, results in our formation, our growth, and all our activities. Even thinking about proton and electron transfer, as you are now, involves them. Here I consider the transfer of a proton in some straightforward reactions in preparation for seeing later, in the second part of the book, how the same processes result in eating, growing, reproducing, and thinking. For reactions that involve the transfer of electrons, see Reaction 5. What is a proton? For physicists, a proton is a minute, positively charged, very stable cluster of three quarks; they denote it p. For chemists, who are less concerned with ultimate things, a proton is the nucleus of a hydrogen atom; they commonly denote it H+ to signify that it is a hydrogen atom stripped of its one electron, a hydrogen ion. I shall flit between referring to this fundamental particle as a proton or a hydrogen ion as the fancy takes me: they are synonyms and the choice of name depends on convention and context. An atom is extraordinarily small, but a proton is about 100 000 times smaller than an atom. If you were to think of an atom as being the size of a football stadium, then a proton would be the size of a fly at its centre. It is nearly 2000 times as heavy as an electron. Nevertheless, a proton is still light and nimble enough to be able to slip reasonably easily out from its home at the centre of a hydrogen atom in some types of hydrogen-containing molecules. Less

When a Daring Chemistry Meets a Boring Chemistry: The Reception of Mendeleev’s Periodic System in Sweden

Anders Lundgren

in Early Responses to the Periodic System

The reception of Mendeleev’s periodic system in Sweden was not a dramatic episode. The system was accepted almost without discussion, but at the same time ... More

The reception of Mendeleev’s periodic system in Sweden was not a dramatic episode. The system was accepted almost without discussion, but at the same time with no exclamation marks or any other outbursts of enthusiasm. There are but a few weak short-lived critical remarks. That was all. I will argue that the acceptance of the system had no overwhelming effect on chemical practice in Sweden. At most, it strengthened its characteristics. It is actually possible to argue that chemistry in Sweden was more essential for the periodic system than the other way around. My results might therefore suggest that we perhaps have to reevaluate the role of Mendeleev’s system in the history of chemistry. Chemistry in Sweden at the end of the nineteenth century can be characterized as a classifying science, with chemists very skilled in analysis, and as mainly an atheoretical science, which treated theories at most only as hypothesis—the slogan of many chemists being “facts persist, theories vanish.” Thanks to these characteristics, by the end of the nineteenth century, chemistry in Sweden had developed into, it must be said, a rather boring chemistry. This is obviously not to say that it is boring to study such a chemistry. Rather, it gives us an example of how everyday science, a part of science too often neglected but a part that constitutes the bulk of all science done, is carried out. One purpose of this study is to see how a theory, considered to be important in the history of chemistry, influenced everyday science. One might ask what happened when a daring chemistry met a boring chemistry. What happened when a theory, which had been created by a chemist who has been described as “not a laboratory chemist,” met an atheoretical experimental science of hard laboratory work and, as was said, the establishment of facts? Furthermore, could we learn something about the role of the periodic system per se from the study of such a meeting? Mendeleev’s system has often been considered important for teaching, and his attempts to write a textbook are often taken as the initial step in the chain of thoughts that led to the periodic system. Less

Robert Boyle’s Corpuscular Chemistry: Atomism before Its Time

Alan Chalmers

in Essays in the Philosophy of Chemistry

In her important and pioneering work on Robert Boyle’s contributions to chemistry Marie Boas Hall (Boas 1958; and Hall 1965, 81–93) portrayed Boyle’s ... More

In her important and pioneering work on Robert Boyle’s contributions to chemistry Marie Boas Hall (Boas 1958; and Hall 1965, 81–93) portrayed Boyle’s advances as being tied up with and facilitated by his adoption of the new world view, the mechanical or corpuscular philosophy, as opposed to Aristotelian or Paracelsian philosophies or world views. In recent decades such a reading has been challenged. Historians of chemistry such as Frederic L. Holmes (1989), Ursula Klein (1994, 1995, 1996) and Mi Gyung Kim (2003) have portrayed modern chemistry as emerging in the seventeenth century by way of a path closely tied to technological and experimental practice and relatively independent of overarching philosophies or world views. Such a perspective raises questions about how productive Boyle’s attempts to wed chemistry and the mechanical philosopher were as far as the emergence of modern chemistry is concerned. This is the issue I will investigate. In recent work on Boyle’s chemistry William Newman (2006) has also taken issue with what he calls the “traditional accounts,” especially that of Hall. Newman’s quarrel with the traditional accounts is the extent to which they read Boyle’s corpuscular chemistry as emerging out of the atomism of Democritus and Lucretius and its reincarnations in the hands of early mechanical philosophers such as Descartes and Gassendi, neglecting a corpuscular tradition that has its origins in Aristotle’s Meteorology. In a range of detailed and pioneering studies Newman (1991, 1996, 2001, 2006) has documented the elaboration of the latter tradition in the works of the thirteenth century author known as Geber and its passage to Boyle, especially via Daniel Sennert, a Wittenburg professor of medicine in the early seventeenth century. While Newman’s work has led to a substantial and significant re-evaluation of the sources of Boyle’s corpuscular chemistry there is a sense in which he does not break from the “traditional” view insofar as he reads the revolutionary aspects of Boyle’s chemistry in terms of a change from an Aristotelian to a mechanical matter theory. Less

Alkali atoms and laser cooling

Massimo Inguscio and Leonardo Fallani

in Atomic Physics: Precise Measurements and Ultracold Matter

This chapter starts with the spectrum of alkali atoms, which have a very similar electronic structure to hydrogen. It describes the hyperfine structure of alkali atoms in the context of the ... More

This chapter starts with the spectrum of alkali atoms, which have a very similar electronic structure to hydrogen. It describes the hyperfine structure of alkali atoms in the context of the development of microwave atomic clocks that currently provide the definition of the SI second. The simple and accessible electronic transitions of alkali atoms were used for the first demonstration of laser cooling, the revolutionary approach to atomic physics developed in the '80s, which the chapter discusses with a review of its most important configurations (optical molasses, magneto-optical traps, sub-Doppler cooling). The application of laser cooling to the development of very precise atomic clocks and to the field of atom interferometry is also covered.Less

The Nobel Laureate

in Science and Conscience: The Life of James Franck

In 1926, James Franck went to Stockholm to receive the 1925 Nobel Prize in physics, which he shared with Gustav Hertz for their experiments supporting Neil Bohr's theory of the atom. He then began to ... More

In 1926, James Franck went to Stockholm to receive the 1925 Nobel Prize in physics, which he shared with Gustav Hertz for their experiments supporting Neil Bohr's theory of the atom. He then began to investigate absorption spectra of alkali halides with Heinrich Kuhn and Günter Rollefson. Franck, Born, and Pohl founded a regional branch of the German Physical Society, the Gauverein Niedersachsen der Deutschen Physikalischen Gesellschaft and they spoke about their research on adsorption catalysis in its semi-annual conventions.Less

Experimental Survey I: The Periodic Table

Kamran Behnia

in Fundamentals of Thermoelectricity

This chapter is devoted to a survey of elemental solids. It begins by comparing the Seebeck coefficient of a metal (cooper), a semi-metal (bismuth) and a semiconductor (silicon). Monovalent metallic ... More

This chapter is devoted to a survey of elemental solids. It begins by comparing the Seebeck coefficient of a metal (cooper), a semi-metal (bismuth) and a semiconductor (silicon). Monovalent metallic (i.e. alkali and noble) are expected to be most akin to a free electron gas. However, this is not the case. Giant enhancement of thermoelectric response by adding a small amount of magnetic impurities is a known signature of Kondo effect. The puzzle of positive Seebeck coefficient of noble metals and the proposed solutions to this puzzle are reviewed. The chapter ends by a discussion of thermoelectric data obtained on elements of column-V (such as bismuth) and column IV (such as silicon).Less