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Introduction
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
In order to decide which method is suitable, it is first necessary to decide what class of compound is being named: ionic or covalent. Recall that ionic compounds are made up of a metal and a nonmetal, where one or more electrons have been effectively transferred from one atom to another. For example, salts, such as sodium chloride or potassium sulfide, are ionic compounds. Covalent compounds are made up of two nonmetals; examples are carbon dioxide and phosphorous pentachloride. Covalent compounds are characterized by covalent bonds, in which electrons are shared between two atoms. If the sharing is unequal, the bond is said to be polar covalent, and one end of the molecule has a partial negative charge. Such molecules are referred to as dipolar and have dipole moments, which are quantitative measures of their polarity. [Higher-order polarities, such as quadrupoles (e.g. in CO2) and hexadecapoles (e.g., in SF6) do exist and can be calculated but are usually small and make an insignificant contribution to the net polarity.] If the sharing is equal, the bond is said to be nonpolar covalent; the molecule has no charge separation and hence no positive or negative end.
Terms and Definitions
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
Ionic compounds bond ionically, that is, there is a positively charged ion (a cation) and a negatively charged ion (an anion). They stick together like two magnets. Metals from the left side of the periodic table form cations and elements from the right side of the periodic table form anions. Sometimes several atoms form a complex ion with a net positive or negative charge. Since it is the entire ion that carries the charge, several negative atoms can overcome the positive charge of a single metal cation. This allows some metals to exist as part of a complex anion such as chromate (CrO4–2) or permanganate (MnO4–).
Potentiometry: pH and Ion-Selective Electrodes
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Ronita L. Marple, William R. LaCourse
Crystalline membrane electrodes are made from an ionic compound (single crystal) or a homogeneous mixture of ionic compounds (polycrystalline). Most of these ionic compounds are insulators, having little or no conductivity at room temperature. Those that are conductive have small, singly charged ions that are mobile in the solid phase.
Modeling the very broad band dielectric properties of water
Published in Journal of Microwave Power and Electromagnetic Energy, 2021
Many materials, which are regularly processed with radio frequency (RF), microwave (MW), and millimeter wave (mm-wave) energy contain both bound and free water. Water is the most abundant substance on earth’s surface (Cabane and Vuilleumier 2005) and has been very well studied. Liquid water has extraordinary properties:It has a very high cohesion, which manifests itself through high melting and boiling temperatures, a high surface tension and a large specific heat, in spite of the molecular weight of water being relatively small (Cabane and Vuilleumier 2005);Because water molecules have a high polar moment, liquid water has an extremely strong response to electric fields. Therefore, liquid water can readily disassociate the individual ions in ionic compounds and hold their ions in solution between the water molecules (Cabane and Vuilleumier 2005). For NaCl, up to 6 mol of salt can be dissolved into 55 mol of water. At this composition, the solution has only 9 molecules of water per ion pair (Cabane and Vuilleumier 2005); andIt is also evident that the structure of water, even as a liquid, is full of voids, especially at low temperatures (Cabane and Vuilleumier 2005). The volume that is occupied by the atoms of the water molecule is 0.0146 nm3, whereas the volume per molecule in liquid water is 0.02992 nm3. The ratio of these volumes is only 0.49, whereas a dense packing of spherical molecules would yield a ratio of 0.74.
Research on treatment of oil-based drill cuttings based on ionic liquids synergistic solvent extraction
Published in Journal of Environmental Science and Health, Part A, 2023
Ionic liquids (ILs) are salts that are liquid at room temperature or close to room temperature. It is an ionic compound composed entirely of anions and cations.[14–16] Therefore, ILs’ physical and chemical properties can be improved by changing the anion and cation or fine-tuning the alkyl chain of the cation.[17,18] According to the different cations, ILs are divided into four categories: imidazoles, quaternary ammonium salts, quaternary phosphines, and pyridines. Imidazole ILs are primarily used in organic synthesis, catalysis, extraction, and separation.[19] There are three primary reasons for choosing ILs. Safety and environmental protection: it has ultra-low saturated vapor pressure and is not volatile,[20] reducing the environmental pollution of volatile organic solvents.[21]Extraction performance: Ionic liquid is an ionic compound, which has a faster dispersion speed in the system, and its dispersion coefficient is several orders of magnitude higher than that of general organic solvents, which can achieve rapid separation of oil–water–solid three phases.Extraction cost: the solubility of ILs can be significantly changed by adding a minimal amount of regulators.[22,23] With this feature, it is easy to separate the ILs from the oil phase and achieve reuses.
The effect of single and combined coagulation/flocculation methods on the sedimentation behavior and conductivity of bentonite suspensions with different swelling potentials
Published in Particulate Science and Technology, 2019
The conductivity of the Ca and Na bentonite suspensions were 834 and 279 µS/cm, respectively, at their natural states. This showed that the ions in the Na bentonite had a limited passage to suspension with low solubility. While the Ca bentonite particles were suspend in an aggregated form of several unit layers due to the bivalent calcium ions, the Na bentonite particles do this in the form of a unit layer (Kim and Palomino 2009). In addition, the conductivity difference between these minerals is related to a higher swelling and water holding capacity of the Na bentonite. Conductivity falls as the water content in the structure rises. The electrical conductivity of clays depends on the volume conductivity (∼water content and composition) and on surface conductivity (∼diffuse double layer, DDL; e.g.,) (Tabbagh and Cosenza 2007; Kaufhold et al. 2015). The conductivity values decrease for all coagulants—especially in lower concentrations because the Na bentonite did not effectively precipitate, and the particles were suspended. The conductivity increased as the amount of coagulants included in the suspension increased. Salts are ionic compounds, and form (+) and (-) charges when dissolved in water; hence, they contribute to electrical conductivity. During coagulation, anions remain in the solution while cations are adsorbed onto the particle surface. As a result, conductivity increases with increasing coagulant concentration. Electrical conductivity indicating the dissolved mineral content of the water; in other words, it reflects the ionic strength. Water conductivity depends on total and relative concentration as well as mobility and valency of the ions in the water. NaCl is the coagulant with the highest increased conductivity of suspension (Figure 3a,b). NaCl is an alkali metal salt, and alkali metal salts (except lithium) are 100% separated into their ions. Thus, they produce more ions than other metal salts, and they increase the conductivity of the medium the most. In addition, other coagulants are found at a lower level in the ionic form within the suspension because they form a precipitate during coagulation. As a result, NaCl increases the electrical conductivity. The flocculant concentration did not affect suspension conductivity (Figure 4a,b).