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(kăt'ī`ən), atom or group of atoms carrying a positive charge. The charge results because there are more protons than electrons in the cation. Cations can be formed from a metal by oxidation (see oxidation and reductionoxidation and reduction,
complementary chemical reactions characterized by the loss or gain, respectively, of one or more electrons by an atom or molecule. Originally the term oxidation
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), from a neutral base (see acids and basesacids and bases,
two related classes of chemicals; the members of each class have a number of common properties when dissolved in a solvent, usually water. Properties
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) by protonation, or from a polar compound by ionization. Cationic species include Na+, Mg++, and NH4+. The cations of the transition elementstransition elements
or transition metals,
in chemistry, group of elements characterized by the filling of an inner d electron orbital as atomic number increases.
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 have characteristic colors in water solution. Saltssalt,
chemical compound (other than water) formed by a chemical reaction between an acid and a base (see acids and bases). Characteristics and Classification of Salts

The most familiar salt is sodium chloride, the principal component of common table salt.
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 are made up of cations and anionsanion
, atom or group of atoms carrying a negative charge. The charge results because there are more electrons than protons in the anion. Anions can be formed from nonmetals by reduction (see oxidation and reduction) or from neutral acids (see acids and bases) or polar compounds
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. See ionion,
atom or group of atoms having a net electric charge. Positive and Negative Electric Charges

A neutral atom or group of atoms becomes an ion by gaining or losing one or more electrons or protons.
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A positively charged atom or group of atoms, or a radical which moves to the negative pole (cathode) during electrolysis.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


a positively charged ion; an ion that is attracted to the cathode during electrolysis
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005


(1) (IDL On the Net) See IDL.

(2) (ION) An NVIDIA graphics platform typically used in Atom-based netbooks. See Intel Atom.

(3) An ion is an atom with fewer or greater electrons than normal as a result of radiation or chemical reaction. A positive ion, called a "cation" (pronounced "cat-eye-en"), has one or more electrons stripped out, which means it has fewer electrons in its electron shells than it has protons in its nucleus. A negative ion, called an "anion" (pronounced "an-eye-en"), is an atom that has one or more electrons forcibly added.

Cations, Anions, Cathodes and Anodes
Although one might think cations are in cathodes and anions are in anodes, the opposite is true. When the terms were coined, the concept was that positive cations were attracted to the negative cathode, and negative anions were attracted to the positive anode.

Batteries Contain Positive and Negative Ions
In a battery, there are positive ions on one side and negative ions on the other. When a conductor is placed in between to complete the circuit, the electrons flow from the negative ions to the positive side where they join the positive ions. See ion deposition.
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References in periodicals archive ?
Meantime, cations like [Na.sup.+] or [Ca.sup.2+] can be filled into the interlayer space to balance the charge, ascribed to the weak interaction force, such as Van de Waals force, between them.
In formation evaluation, it is the contribution of cation exchange sites to the formation of electrical properties that is important or required to determine the clay types and dry clay parameters.
The scientists show that the guanidinium cation inserts into the crystal structure of the perovskite and enhances the material's overall thermal and environmental stability, overcoming what is known in the field as the "Goldschmidt tolerance factor limit." This is an indicator of the stability of a perovskite crystal, which describes how compatible a particular ion is to it.
Herein, we report our studies for mixed-cation perovskites using aromatic ammoniums with various linkers between the aromatic ring and the ammonium cation. In particular, a surprising effect of the bulky cations onto the photoluminescence (PL) properties is disclosed.
In this paper we present the results from MD simulations for the basal spacing of Na-, K-, and Ca-montmorillonites and the density profiles and snapshots of cations and oxygen-water atoms in the interlayer region.
However, the ECR as proposed in Rengasamy and Marchuk (2011) does not provide for specific dispersive effects of exchangeable K and Mg cations. Hence, there is currently no equivalent equation to explain soil dispersion on the basis of specific exchangeable cation effects.
Building on earlier conceptual work by Rengasamy and Sumner (1998), Rengasamy and Marchuk (2011) have proposed a generalization of SAR which quantifies both the differing effects of Na and K as dispersing cations diminishing soil permeability and the differing effects of Mg and Ca as flocculating cations enhancing soil permeability.
It is well known that crown ether is a very good chelator for alkaline cations, the co-complexed alkaline cations could approach the central cobalt ions, which is useful for influencing its oxygen-binding capability.
In this work, we propose that appearance of overshooting effect may be attributed to the chelation between cations and the anionic groups on the polymer chains, which leads to the variation of crosslinking degree and the reorganization of the gel structure.
The need for selective reagents and processes for species with similar chemical properties still renders the investigations on the interaction of metal cations with macrocyclic ligands.
The main objective of this research was to convert rice husk and canola stalk to activated carbon and also evaluation of their sorption capacity to remove Ca and Mg as main cations causing hardness.
Recently, new polymerizable 1,8-naphthalimide molecules to sensitive protons or metal cations have been synthesized and their functional properties are investigated.