Complex compounds are molecular compounds which retain their identities even when dissolved in water β Coordination Compounds Chemistry Question
Question
Complex compounds are molecular compounds which retain their identities even when dissolved in water. They do not give all the simple ions in solution but instead furnish complex ions. The complex compounds are often called coordination compounds because certain groups called ligands are attached to the central metal ion by coordinate or dative bonds. Coordination compounds exhibit isomerism, both structural and stereoisomerism. The structure, magnetic property, colour and electrical properties of complexes are explained by various theories.

π‘ Solution & Explanation
Step 1: Ammonia (NH3) is a Lewis base that coordinates to copper ions through the lone pair of electrons on its nitrogen atom. Step 2: In acidic solutions, the high concentration of protons (H^+) causes ammonia to undergo protonation to form the ammonium ion (NH4^+). Step 3: Because NH4^+ lacks a lone pair of electrons, it cannot coordinate to Cu^2+ ions. Therefore, ammonia coordinates with protons instead of forming the complex, which corresponds to option (d).