CUET Preparation Today
Which of the following postulates of Werner theory is incorrect? |
In coordination compounds metals show two types of linkages (valences)-primary and secondary. The primary valences are normally ionisable and are satisfied by negative ions. The secondary valence is equal to the oxidation number of metal and is fixed for a metal. The ions/groups bound by the secondary linkages to the metal have characteristic spatial arrangements corresponding to different coordination numbers. |
The secondary valence is equal to the oxidation number of metal and is fixed for a metal. |
The correct answer is Option (3) → The secondary valence is equal to the oxidation number of metal and is fixed for a metal. Werner proposed that metals exhibit two types of valencies: • Primary valency → Equal to oxidation state , Ionisable , Satisfied by negative ions • Secondary valency → Equal to coordination number , Non-ionisable , Fixed spatial arrangement Important: Primary valency = Oxidation state Secondary valency = Coordination number They are NOT the same. Option 1: In coordination compounds metals show two types of linkages (valences)-primary and secondary. This is a correct postulate of Werner theory. Option 2: Primary valencies are ionisable and satisfied by negative ions. Correct according to Werner’s theory. Option 3: States that secondary valency equals oxidation number. This is incorrect. Secondary valency = Coordination number Primary valency = Oxidation number Hence this statement is wrong Option 4: The ions/groups bound by the secondary linkages to the metal have characteristic spatial arrangements corresponding to different coordination numbers. Correct postulate. |
