Properties Of Individual Atoms Research Articles

A view about the short histories of the mole and Avogadro’s number

The mole and Avogadro’s number are two important concepts of science that provide a link between the properties of individual atoms or molecules and the properties of bulk matter. It is clear that an early theorist of the idea of these two concepts was Avogadro. However, the research literature shows that there is a controversy about the subjects of when and by whom the mole concept was first introduced into science and when and by whom Avogadro’s number was first calculated. Based on this point, the following five matters are taken into consideration in this paper. First, in order to base the subject matter on a strong ground, the historical development of understanding the particulate nature of matter is presented. Second, in 1811, Amedeo Avogadro built the theoretical foundations of the mole concept and the number 6.022 × 1023 mol−1. Third, in 1865, Johann Josef Loschmidt first estimated the number of molecules in a cubic centimetre of a gas under normal conditions as 1.83 × 1018. Fourth, in 1881, August Horstmann first introduced the concept of gram-molecular weight in the sense of today’s mole concept into chemistry and, in 1900, Wilhelm Ostwald first used the term mole instead of the term ‘gram-molecular weight’. Lastly, in 1889, Karoly Than first determined the gram-molecular volume of gases under normal conditions as 22,330 cm3. Accordingly, the first value for Avogadro’s number in science history should be 4.09 × 1022 molecules/gram-molecular weight, which is calculated by multiplying Loschmidt’s 1.83 × 1018 molecules/cm3 by Than’s 22,330 cm3/gram-molecular weight. Hence, Avogadro is the originator of the ideas of the mole and the number 6.022 × 1023 mol−1, Horstmann first introduced the mole concept into science/chemistry, and Loschmidt and Than are the scientists who first calculated Avogadro’s number. However, in the science research literature, it is widely expressed that the mole concept was first introduced into chemistry by Ostwald in 1900 and that Avogadro’s number was first calculated by Jean Baptiste Perrin in 1908. As a result, in this study, it is particularly emphasised that Horstmann first introduced the mole concept into science/chemistry and the first value of Avogadro’s number in the history of science was 4.09 × 1022 molecules/gram-molecular weight and Loschmidt and Than together first calculated this number.

Nanotechnology in therapeutic sciences: Possible risks and benefits

Nanotechnology is the design, characterization, production, and application of structures, devices and systems by controlling the shape and size at the nanometer scale. Since at nanoscale, the properties of materials differ in fundamental and valuable ways from the properties of individual atoms and molecules or bulk matter, nanotechnology has a wide-range of applications in different fields such as electronics, pharmaceuticals, materials, polymers, chemical and petroleum industry. This article aims to review the benefits and hazards of nano-particles in Therapeutic sciences. As the need for the development of new medicine is pressing, and given the inherent nanoscale functions of biological components of living cells, nanotechnology has been applied to diverse medical fields such as oncology, cardiovascular medicine and in the treatment of other chronic diseases. Indeed, nanotechnology is being used to refine discovery of biomarkers, molecular diagnostics, and drug delivery, which could be applicable to management of these patients. The ideal nanopharmaceuticals agent must be safe, biocompatible, biodegradable, and stealthy-disguised well enough that the body's immune system will not recognize it as foreign. The ultimate agent will recognize the toxic molecules, attract and bind them quickly, reduce the free drug concentration and in the process, trigger the heart to function normally. On the other hand, very small size appears to be predominant indicator for toxic effects of particle. For medical applications, immobilized nanostructure inside or on surfaces of medical devices such as surgical implants are expected to pose a minimal risk as long as they remain fixed. As for Nanopharmaceuticals, they can act on living cells at the nano level resulting not only in biologically desirable, but also in undesirable effects. From a regulatory point of view, a risk management strategy is already a requirement for all medical technology applications.

A Review of Reliability Research on Nanotechnology

Nano-reliability measures the ability of a nano-scaled product to perform its intended functionality. At the nano scale, the physical, chemical, and biological properties of materials differ in fundamental, valuable ways from the properties of individual atoms, molecules, or bulk matter. Conventional reliability theories need to be restudied to be applied to nano-engineering. Research on nano-reliability is extremely important due to the fact that nano-structure components account for a high proportion of costs, and serve critical roles in newly designed products. This review introduces the concepts of reliability to nano-technology; and presents the current work on identifying various physical failure mechanisms of nano-structured materials, and devices during fabrication process, and operation. Modeling techniques of degradation, reliability functions, and failure rates of nano-systems are also reviewed in this work.

Probing magnetic properties of atoms with STM

The magnetic properties of individual atoms adsorbed on metal and insulating substrates can differ dramatically. While an atom on an insulating substrate can maintain some basic properties such as a free spin, such a free spin is strongly screened by a metal's conduction electrons when the atom is placed directly on the metal. This screening gives rise to the Kondo effect. Scanning Tunneling Microscopy was used to probe the magnetic properties of atoms adsorbed on metals and thin insulating substrates. We find spin-flip spectroscopy for Mn adsorbed on thin aluminum oxide with no sign of Kondo effect. On the other hand Co atoms on Cu substrates show a clear Kondo resonance around the Fermi energy with no sign of spin-flip spectroscopy. Mn atoms very close to the edge of an aluminum oxide patch can recover the Kondo effect albeit with very small Kondo temperatures because of their relative proximity to the conduction electrons of the underlying metal. [DOI: 10.1380/ejssnt.2006.384]

Quantum Theory of Collective Phenomena: Monographs on the Physics and Chemistry of Materials

G L Sewell 1986 Oxford: Oxford University Press xiii + 229 pp price £35 ISBN 0 19 851371 2 Many macroscopic phenomena (phase transitions being the prime example) are not easily amenable to a quantum mechanical treatment. The reason is that, although quantum mechanical in nature, they are also collective: they involve the cooperation of a very large number of particles and cannot merely be reduced to the properties of individual atoms and molecules.

Incidence and distance matrices

It is now recognised that many aspects of chemistry are, in some considerable measure, topologically determined. For example, graph theory has been applied to problems in Valence Theory an aspect which has been explored by several authors.1,2,3*4 Perhaps the earliest application of formal graph theory to a chemistry problem was Cayley’s work in determining the isomer counts of the paraffinic hydrocarbons.’ A much more recent application also concerns isomers and is the subject of the present communication. Fluxional (stereochemically non-rigid) molecules, undergo rapid molecular rearrangements. All the isomers have the same equilibrium geometry and differ only in atomic permutations, but on a nuclear magnetic resonance time scale the properties of individual atoms may be a time average of those associated with mote than one position. Although is not always possible to associate a unique permutation with a unique permutational mechanism each species has a definite number of permutational isomer?j’ each permutational mechanism leading to a characteristic pattern of interconversions between these isomers. The various mechanisms are conveniently distinguished by the different shortest path sequences by which any given isomer is converted into another. The shortest paths are detailed in a so-called distance matrix of the system, examples of which have been given by several authors. However there appears to be in the chemical literature no details of the derivation of such matrices. It is the purpose of the present communication to remedy this ommision and to propose some innovations that will increase the information content of them.