Read the passage carefully and answer the Questions.

Werner in 1898, propounded his theory of coordination compounds. 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 valences are non-ionisable. These are satisfied by neutral molecules or negative ions. The secondary valence is equal to the coordination number and is fixed for a metal. The ions or group bound by the secondary linkages to the metal have characteristic spatial arrangements corresponding to the different coordination numbers. Both double salts as well as complexes are formed by the combination of two or more stable compounds in stoichiometric ratio. However, they differ in the fact that double salts such as carnallite, Mohr's salt, potash alum etc. dissociate into simple ions completely when dissolved in water. But complex ions do not dissociate completely into simple ions.

Which of the following statement is correct as per Werner theory?

the number of groups bound directly to the metal ion corresponding to the coordination number are Secondary valences

The correct answer is Option (2) → the number of groups bound directly to the metal ion corresponding to the coordination number are Secondary valences

According to Werner’s coordination theory, the correct statements are:

Key Points of Werner’s Theory

• Primary valence = oxidation state; ionisable.
• Secondary valence = coordination number; non-ionisable.
• Groups bound directly to the metal (ligands) satisfy secondary valence.

Evaluate the options:

Option A: Secondary valences are ionisable.

❌ Incorrect — secondary valences are non-ionisable.

Option B: The number of groups bound directly to the metal ion corresponding to the coordination number are Secondary valences

✅ Correct — this matches Werner's theory.

Option C: Primary valences are non-ionisable

❌ Incorrect — primary valences are ionisable.

Option D: Primary valences correspond to the coordination number of the metal

❌ Incorrect — they correspond to oxidation state, not coordination number.