cation
(noun)
A positively charged ion, as opposed to an anion.
(noun)
A positively charged ion.
(noun)
Ions that are positively charged because they have more protons than electrons.
Examples of cation in the following topics:
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Cationic Chain-Growth Polymerization
- Polymerization of isobutylene (2-methylpropene) by traces of strong acids is an example of cationic polymerization.
- Monomers bearing cation stabilizing groups, such as alkyl, phenyl or vinyl can be polymerized by cationic processes.
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Ionic Radius
- Ionic radius (rion) is the radius of an ion, regardless of whether it is an anion or a cation.
- In this way, the sum of ionic radii of a cation and an anion can give us the distance between the ions in a crystal lattice.
- Note that this only applies if the elements are the same type of ion, either cations or anions.
- For example, while neutral lithium is larger than neutral fluorine, the lithium cation is much smaller than the fluorine anion, due to the lithium cation having a different highest energy shell.
- The neutral atoms are colored gray, cations red, and anions blue.
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Characteristics of Mass Spectra
- Loss of a hydrogen atom, either before or after ring opening, produces the stable allyl cation (m/z=41).
- The molecular ion in a mass spectrum is always a radical cation, but the fragment ions may either be even-electron cations or odd-electron radical cations, depending on the neutral fragment lost.
- Most of the fragment ions have odd-numbered masses, and therefore are even-electron cations.
- The weak even -electron ions at m/z=15 and 29 are due to methyl and ethyl cations (no nitrogen atoms).
- Bond cleavage generates a radical and a cation, and both fragments often share these roles, albeit unequally.
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Naming Ionic Compounds
- An ionic compound is named first by its cation and then by its anion.
- An ionic compound is named first by its cation and then by its anion.
- The cation has the same name as its element.
- To name a compound, the cation name and the anion named are added together.
- Since some metallic elements form cations that have different positive charges, the names of ionic compounds derived from these elements must contain some indication of the cation charge.
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Salts that Produce Acidic Solutions
- This is due either to the presence of a metal cation that acts as a Lewis acid (which will be discussed in a later concept), or, quite commonly, due to a hydrolyzable proton in the cation or the anion.
- Salts with acidic protons in the cation are most commonly ammonium salts, or organic compounds that contain a protonated amine group.
- An example of an acid salt is one containing any of these cations with a neutral base, such as ammonium chloride (NH4Cl).
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Chemical Analysis
- Cations are usually classified into one of six groups according to their properties, while anions are classified into one of three groups.
- Each group has a common reagent that can be used to separate the cation or anion from a solution.
- This happens because cationic analysis is based on the solubility products of the ions.
- As the cation achieves the optimum concentration needed, it precipitates, allowing detection.
- (While many of the earlier cations will precipitate with carbonate, they will have been detected prior to this point if the steps have been followed in order.)
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Ionic Bonding and Electron Transfer
- Ionic bonds involve a cation and an anion.
- The bond is formed when an atom, typically a metal, loses an electron or electrons, and becomes a positive ion, or cation.
- In this video, Paul Andersen explains how ionic solids form when cations and anions are attracted.
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Oxidation
- When silver cation is the oxidant, as in the above equation, it is reduced to metallic silver in the course of the reaction, and this deposits as a beautiful mirror on the inner surface of the reaction vessel.
- The Fehling and Benedict tests use cupric cation as the oxidant.
- All these cation oxidations must be conducted under alkaline conditions.
- To avoid precipitation of the insoluble metal hydroxides, the cations must be stabilized as complexed ions.
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Complex Ion Equilibria and Solubility
- Formation of a complex ion between a metal cation and a ligand can increase salt solubility.
- A complex ion is an ion comprising one or more ligands attached to a central metal cation with a dative bond.
- Cations of d-block metals (transition metals) are small, have a high charge, and have available empty 3d and 4s orbitals of low energy.
- The number of lone pairs of electrons a cation can accept is known as the coordination number of the cation.
- This number depends on the size and electronic configuration of that cation and on the size and charge of the ligand.
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Overview of the Acid-Base Properties of Salt
- Some salts, such as ammonium bicarbonate (NH4HCO3), contain cations and anions that can both undergo hydrolysis.
- As we have discussed, salts can form acidic or basic solutions if their cations and/or anions are hydrolyzable (able to react in water).
- The following is a more complicated scenario in which a salt contains a cation and an anion, both of which are capable of participating in hydrolysis.
- Predict the pH of a solution of a salt containing cations and anions, both of which participate in hydrolysis.