Search results
Results From The WOW.Com Content Network
In condensed matter physics and inorganic chemistry, the cation-anion radius ratio can be used to predict the crystal structure of an ionic compound based on the relative size of its atoms. It is defined as the ratio of the ionic radius of the positively charged cation to the ionic radius of the negatively charged anion in a cation-anion compound.
For typical ionic solids, the cations are smaller than the anions, and each cation is surrounded by coordinated anions which form a polyhedron.The sum of the ionic radii determines the cation-anion distance, while the cation-anion radius ratio + / (or /) determines the coordination number (C.N.) of the cation, as well as the shape of the coordinated polyhedron of anions.
4, it is usually assumed that the cation is the reactive agent and this tetrahedral anion is inert. BF − 4 owes its inertness to two factors: (i) it is symmetrical so that the negative charge is distributed equally over four atoms, and (ii) it is composed of highly electronegative fluorine atoms, which diminish the basicity of the anion.
Relative radii of atoms and ions. The neutral atoms are colored gray, cations red, and anions blue. Ions may be larger or smaller than the neutral atom, depending on the ion's electric charge. When an atom loses an electron to form a cation, the other electrons are more attracted to the nucleus, and the radius of the ion gets smaller.
The terms "anion" and "cation" in the bond valence model are defined in terms of the bond topology, not the chemical properties of the atoms. This extends the scope of the ionic model well beyond compounds in which the bonding would normally be considered as "ionic". For example, methane, CH 4, obeys the conditions for the ionic model with ...
In these the locations of the anions and cations are reversed relative to fluorite (an anti-structure); the anions occupy the FCC regular sites whereas the cations occupy the tetrahedral interstitial sites. For example, magnesium silicide, Mg 2 Si, has a lattice parameter of 6.338 Å with magnesium cations occupying the tetrahedral interstitial ...
Assume the chemical composition is AX, with A being the cation and X being the anion. (The following assumes that X is a diatomic gas such as oxygen and therefore cation A has a +2 charge. Note that materials with this defect structure are often used in oxygen sensors.) In the reduced n-type, there are excess cations on the interstitial sites: A ×
The perrhenate ion is the anion with the formula ReO − 4, or a compound containing this ion. The perrhenate anion is tetrahedral, being similar in size and shape to perchlorate and the valence isoelectronic permanganate. The perrhenate anion is stable over a broad pH range and can be precipitated from solutions with the use of organic cations.