What is Isodesmic bond?

An isodesmic reaction is a chemical reaction in which the type of chemical bonds broken in the reactant are the same as the type of bonds formed in the reaction product. This type of reaction is often used as a hypothetical reaction in thermochemistry.

What does Mesodesmic mean?

Isodesmic – all bonds have same relative strength. Mesodesmic – cation-anion bond strength = ½ charge, meaning identical bond strength available for further bonding to cation or other anion.

What is a mineral and how does Pauling’s rule relate to mineralogy?

Pauling’s first rule, sometimes called the Radius Ratio Principle, states that the distance between cations and anions can be calculated from their effective ionic radii, and that cation coordination number depends on the relative ratio of cation and surrounding anion radii.

What is the coordination of halite?

atoms surrounding each Na atom in octahedral coordination in the array of atoms in halite.

Is Graphite an Isodesmic?

An isodesmic crystal is a crystal in which all the bonds have the same electrostatic valency. Graphite is an example of an anisodesmic crystal.

What is the coordination number of fluorite?

In the fluorite structure, the cation site (Ca2+) is surrounded by a cubic array of eight F anions, and the anions (F-) in theirs tetrahedral holes have four nearest neighbors. So the structure is said to have 8:4 coordination.

What are the five Pauling’s rules and what is the meaning of that rules?

1 First rule: the radius ratio rule. 2 Second rule: the electrostatic valence rule. 3 Third rule: sharing of polyhedron corners, edges and faces. 4 Fourth rule: crystals containing different cations. 5 Fifth rule: the rule of parsimony.

What is 6 fold coordination?

Six-fold coordination is also called octahedral coordination because the shape defined by drawing planes through the center of the larger ions is an octahedron.

Why is Pauling rule important in mineralogy?

This gives us the coordination number of the cation. Even though the rule is stated as being applicable to ionic crystals, it is actually of use whether the bonding is ionic, covalent, or metallic. It tells us what can fit in the closest-packing voids and so on.

What is Pauling’s first rule?

First rule: the radius ratio rule If the cation is smaller, it will not be in contact with the anions which results in instability leading to a lower coordination number.

What is the chemical formula for olivine?

Chemical composition Most of the naturally occurring olivines are intermediate in composition to these two end-members and have the general formula (Mg, Fe)2SiO4.