postulates of warners theory
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ANSWER¶
(i)= Every metal atom has two types of valencies
Primary valency or ionisable valency
Secondary valency or non ionisable valency
(ii)= The primary valency corresponds to the oxidation state of the metal ion.
The primary valency of the metal ion is always satisfied by negative ions.
(iii)=Secondary valency corresponds to the coordination number of the metal ion or atom. The secondary valencies may be satisfied by either negative ions or neutral molecules.
(iv)= The molecules or ion that satisfy secondary valencies are called ligands.
(v)= The ligands which satisfy secondary valencies must project in definite directions in space. So the secondary valencies are directional in nature whereas the primary valencies are non-directional in nature.
(vi)= The ligands have unshared pair of electrons. These unshared pair of electrons are donated to central metal ion or atom in a compound. Such compounds are called coordination compounds.
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Answer:
Explanation:
In 1823, Werner put forth a theory to describe the structure and formation of complex compounds or coordination compounds which won him the Nobel prize as well as the title of “father of coordination chemistry”.
The postulates involved in this theory are:-
1) The central metal or the metal atoms in the coordination show two types of valences primary and secondary valency.
2) The primary valency relates to the oxidation state and the secondary valency relates to the coordinate number.
3) The number of secondary valences is fixed for every metal atom. It means that the coordination number is fixed.
4) The metal atom works towards satisfying both its primary and secondary valences. A negative ion satisfies the primary valency. On the other hand, a negative ion or neutral molecules satisfy secondary valences.
5) The secondary valences point towards a fixed position in space. This is the reason behind the definite geometry of the coordinate compound. For example, let us consider the case of a metal ion having six secondary valences.
These arrange octahedrally around the central metal ion. If the metal ion has four secondary valences, these arrange in either tetrahedral or square planar arrangement around the central metal ion. Therefore, we see that the secondary valency determines the stereochemistry of the complexion. On the other hand, the primary valency is non-directional.