Question

According to Werner’s theory of coordination compounds:
A. primary valency is ionisable.
B. secondary valency is ionisable.
C. primary and secondary valencies are ionisable.
D. neither primary nor secondary valency is ionisable.

Answer 1

Hint: According to Werner's theory, a coordination compound has two different types of valency, primary and secondary. The primary valency or the ionisable valency is satisfied by the negative charged ions in the solution.

Complete step by step answer:
The various postulates of Werner’s theory are:
(i) Every metallic element shows two different types of valencies:
(a) Primary valency- This is ionizable and is satisfied by the negative charges.
(b) Secondary valency- This is non-ionizable and is satisfied by the positive charged or neutral species in the solution.
(ii) Every metal tends to satisfy its primary and secondary valency.
(iii) The number of secondary valence shown by each metal is fixed and the metal can be surrounded by a fixed number of ligands in space.
(iv) The secondary valency is always directed towards fixed spatial orientation in the space.
Now let us understand what the term primary valency and secondary valency signify. The primary valency corresponds to the oxidation state of the metal ion and it is always satisfied by the negative charged ions. The secondary valency corresponds to the coordination number of the metal complex. The molecules or ions that satisfy the secondary valency are called ligands and they can be either negatively charged or neutral.
Thus, the correct option is A i.e primary valency is ionisable.

Note:
Werner stated that in a coordination complex, there lies a coordination sphere which consists of a central metal atom (generally the transition metals) surrounded by the electron donating nucleus seeking species which attack at the vacant orbital sites of the central metal atom.