Question

According to Werner's theory of coordination compounds, the secondary valency represents 

• A. Coordination number
• B. Oxidation state
• C. Charge on the complex
• D. Ionic character
  [10pt]

Hint:

Remember that primary valencies are represented by dotted lines (ionisable oxidation state), whereas secondary valencies are represented by solid lines (non-ionisable coordination number determining spatial geometry).

Answer 1

The Correct Option is A

Step 1: Recall Werner's theory.
Alfred Werner said a metal in a complex has two kinds of valency. One is the primary valency and the other is the secondary valency.
Step 2: Meaning of primary valency.
The primary valency is the ionisable part. It matches the oxidation state or charge of the metal and is met by negative ions.
Step 3: Meaning of secondary valency.
The secondary valency is non ionisable and fixed in direction. It is met by ligands that bond straight to the metal.
Step 4: Link to a modern term.
In modern words, the secondary valency is the same as the coordination number. That is the number of ligand atoms joined to the metal.
Step 5: Rule out the others.
The oxidation state and the charge on the complex come from the primary valency, not the secondary one. So those choices are wrong.
Step 6: Final choice.
So the secondary valency stands for the coordination number.\[ \boxed{\text{Coordination number}} \]