MoleculeA molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and molecule is often used when referring to polyatomic ions. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, e.
Partition coefficientIn the physical sciences, a partition coefficient (P) or distribution coefficient (D) is the ratio of concentrations of a compound in a mixture of two immiscible solvents at equilibrium. This ratio is therefore a comparison of the solubilities of the solute in these two liquids. The partition coefficient generally refers to the concentration ratio of un-ionized species of compound, whereas the distribution coefficient refers to the concentration ratio of all species of the compound (ionized plus un-ionized).
Dust BowlThe Dust Bowl was the result of a period of severe dust storms that greatly damaged the ecology and agriculture of the American and Canadian prairies during the 1930s. The phenomenon was caused by a combination of natural factors (severe drought) and man-made factors: a failure to apply dryland farming methods to prevent wind erosion, most notably the destruction of the natural topsoil by settlers in the region. The drought came in three waves: 1934, 1936, and 1939–1940, but some regions of the High Plains experienced drought conditions for as long as eight years.
Optical mineralogyOptical mineralogy is the study of minerals and rocks by measuring their optical properties. Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope. Optical mineralogy is used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution.
Ion sourceAn ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines. Electron ionization Electron ionization is widely used in mass spectrometry, particularly for organic molecules. The gas phase reaction producing electron ionization is M{} + e^- -> M^{+\bullet}{} + 2e^- where M is the atom or molecule being ionized, e^- is the electron, and M^{+\bullet} is the resulting ion.
Chemical equilibriumIn a chemical reaction, chemical equilibrium is the state in which both the reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the system. This state results when the forward reaction proceeds at the same rate as the reverse reaction. The reaction rates of the forward and backward reactions are generally not zero, but they are equal. Thus, there are no net changes in the concentrations of the reactants and products.
Equilibrium constantThe equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency towards further change. For a given set of reaction conditions, the equilibrium constant is independent of the initial analytical concentrations of the reactant and product species in the mixture.
Surface scienceSurface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fields of surface chemistry and surface physics. Some related practical applications are classed as surface engineering. The science encompasses concepts such as heterogeneous catalysis, semiconductor device fabrication, fuel cells, self-assembled monolayers, and adhesives.
Halide mineralHalide minerals are those minerals with a dominant halide anion (, , and ). Complex halide minerals may also have polyatomic anions. Examples include the following: Atacamite Avogadrite (K,Cs)BF Bararite (β) Bischofite Brüggenite Calomel Carnallite Carnallite Cerargyrite/Horn silver AgCl Chlorargyrite AgCl, bromargyrite AgBr, and iodargyrite AgI Cryolite Cryptohalite (a) Dietzeite Eglestonite Embolite AgCl+AgBr Eriochalcite Fluorite Halite NaCl Lautarite Marshite CuI Miersite AgI Nantokite CuCl Sal Ammoniac Sylvite KCl Terlinguaite Tolbachite Villiaumite NaF Yttrocerite (Ca,Y,Ce)F2 Yttrofluorite (Ca,Y)F2 Zavaritskite (BiO)F Many of these minerals are water-soluble and are often found in arid areas in crusts and other deposits as are various borates, nitrates, iodates, bromates and the like.
Atmospheric electricityAtmospheric electricity describes the electrical charges in the Earth's atmosphere (or that of another planet). The movement of charge between the Earth's surface, the atmosphere, and the ionosphere is known as the global atmospheric electrical circuit. Atmospheric electricity is an interdisciplinary topic with a long history, involving concepts from electrostatics, atmospheric physics, meteorology and Earth science. Thunderstorms act as a giant battery in the atmosphere, charging up the electrosphere to about 400,000 volts with respect to the surface.
