Binary compounds: simple structures, Chemistry

 

Coordination number and geometry

 

Binary compounds are ones with two different elements present. 'Simple' crystal structures can be classed as ones in which each atom (or ion) is surrounded in a regular way by atoms (or ions) of the other kind. Even with this limited existence many structures are possible.

Although many are achieved with ionic compounds, some of these structures are shown by compounds with covalent bonding, and a discussion of the bonding factors involved in favoring one structure rather than another is deferred to

When the two elements B and A are not equivalent A is drawn smaller and with shading. In ionic compounds this is more general the metallic (cationic) element. If the role of cations and anions is reversed we speak of the anti-structure: thus Li2O has the, Cs2O the anti-CdI2 structure and anti-fluorite (CaF2) structure.

From the local point of view of each atom the most important characteristics of a structure are the coordination geometry and coordination number (CN). In the examples described these are the same for all atoms of the same type. Coordination numbers can be compatible with the stoichiometry. In AB both B and A have the same CN, the examples shown being

 

Zinc blende (4:4); Rocksalt (6:6); NiAs (6:6); CsCl (8:8).

 

When the stoichiometry is AB2 the CN of A has to be twice that of B:

Rutile (6:3); CdI2 (6:3); Fluorite (8:4).

 

 

 

 

 

 

2292_Untitled.png

 

 

Fig. 1. A selection of binary structures.

In the structures illustrate many of the atoms have regular coordination geometry:

 

CN=2: linear (B in ReO3);

 

CN=3: planar (B in rutile);

 

CN=4: tetrahedral (A and B in zinc blende, B in fluorite);

 

CN=6: octahedral (A and B in rocksalt, A in NiAs, rutile and CdI2);

 

CN=8: cubic (A and B in CsCl, A in fluorite).

 

Posted Date: 7/23/2012 12:48:36 AM | Location : United States







Related Discussions:- Binary compounds: simple structures, Assignment Help, Ask Question on Binary compounds: simple structures, Get Answer, Expert's Help, Binary compounds: simple structures Discussions

Write discussion on Binary compounds: simple structures
Your posts are moderated
Related Questions
(a) Discuss, with the aid of diagrams, and with suitable examples, the chemistry (including half-cell reactions), construction and principles of the following electrode types: (

What are the physical properties of Glucose?

Chemical Properties Proteins - Salt formation (i) Salt formation : Due  to  existence of  both -NH 2 and -COOH groups in proteins, they make salts along with acids and bases.

what category are Alkali-Metals on the periodic table?

Physical properties of Alkyl cyanides (1) Alkyl cyanides are neutral substance with pleasant odour, similar to bitter almonds. (2) Alkyl cyanides are Lower members containin

#question.why basic radicals are arranged in different groups.

chemical properties of formic acid

The phosphate of a metal has the formula MPO4 .The formula of its nitrate will be: (1) MNO 3                                                   (2)  M 2 (NO 3 ) 2

Q. Explain about Smelting process? The roasted ore, which is generally an oxide, is strongly heated with a suitable reducing agent as result of which the metal is acquired in a

tell me the methods of preparation of nitrenes?