Question

(i) What are the postulates of Werner's theory?
(ii) Write the IUPAC names fo $K_3\left[Fe{\left(CN\right)}_6\right]$, $\left[Co{\left(N{H}_3\right)}_6\right]{Cl}_3$.

Answer 1

i) $\text{Postulates of Werner’s theory}$:

• Every metal atom has two types of valencies
  

i)Primary valency or ionisable valency

ii)Secondary valency or non ionisable valency

• 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.
  
• 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.
  
• The molecules or ion that satisfy secondary valencies are called ligands.
  
• 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.
  
• 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.
  

(ii) $K_3\left[Fe{\left(CN\right)}_6\right]$ is Potassium hexacyanoferrate(III).

$\left[Co{\left(N{H}_3\right)}_6\right]{Cl}_3$.is Hexamminecobalt (III) chloride.