Binary compounds: simple structures, Chemistry

Assignment Help:

 

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).

 


Related Discussions:- Binary compounds: simple structures

Free radical mechanism, define free radical mechanism of additon reaction

define free radical mechanism of additon reaction

How tert-butylamine is prepared, Tert-butylamine Tert-butylamine cannot...

Tert-butylamine Tert-butylamine cannot be prepared by the Gabriel synthesis because it would require that the nitrogen of phthalimide be alkylated with tert-butyl bromide in an

Phenol, what is libermaan''s nitroso reaction .what is mechanism of this re...

what is libermaan''s nitroso reaction .what is mechanism of this reaction

The principal quantum number represents, The principal quantum number repre...

The principal quantum number represents : (1) Shape of an orbital (2) Distance of electron from nucleus (3) Number of electrons in an orbit (4) Number of orbitals in an

Organic, Distinguish between acetaldehyde and ketone

Distinguish between acetaldehyde and ketone

Orsat analysis, Thirty pounds of coal (analysis 80% C and 20% H ignoring th...

Thirty pounds of coal (analysis 80% C and 20% H ignoring the ash) are burned with 600 lbs of air (with a variable humidity), yielding a gas have an Orsat analysis in which the rati

Hardness of water, (a) What is hardness of water? What do you understand ...

(a) What is hardness of water? What do you understand by temporary and permanent hardness?                                                            OR Explain tempora

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd