Question

According to Werner's theory, the primary valencies of the central metal atom :

• A. are satisfied by neutral molecules or negative ions
• B. are equal to its coordination number
• C. are satisfied by negative ions
• D. are non-ionisable

Hint:

Primary valency = the metal's charge, balanced by anions; secondary valency = coordination number.

Answer 1

The Correct Option is C

Step 1: Two kinds of valency.
Werner pictured a metal in a complex as holding on to other groups using two separate kinds of bonding power. One of them depends on the actual charge the metal carries, and the other depends on how many groups crowd around it. We need to decide which of these the question is asking about.

Step 2: What primary valency really means.
The primary valency is nothing more than the oxidation state, that is the net positive charge sitting on the metal ion. A positive charge cannot float around on its own, it has to be balanced by something carrying the opposite charge. That balancing job is done by negative ions placed outside the metal. Because these anions can drift away in water, this valency is the ionisable part of the complex.

Step 3: Keep it separate from secondary valency.
The secondary valency is a different thing, it equals the coordination number and it is satisfied by the ligands attached right next to the metal. Those ligands may be neutral molecules or ions, so options talking about coordination number or neutral molecules are describing the secondary valency, not the one asked here.

Step 4: Choose the answer.
Since the primary valency is the metal's charge that gets neutralised by anions, it is satisfied by negative ions.
\[ \boxed{\text{Option (C): satisfied by negative ions}} \]