Coordination Chemistry

A coordination compound is formed when a central metal ion or atom is surrounded by a number of ligands, which are molecules or ions that can donate electron pairs to the metal ion.
Step 1: Review the options - Option 1: While coordination compounds can have a definite molecular formula, this is not their most distinguishing feature.
- Option 2: Coordination compounds do not necessarily have high melting points or conduct electricity in the solid state. This is more typical of ionic compounds.
- Option 3: The hallmark of a coordination compound is the bonding of a central metal atom/ion with ligands. This option is correct.
- Option 4: Coordination compounds can be soluble in water, especially if they form ions in solution.
Answer: The correct characteristic of a coordination compound is option (3) — it contains a central metal atom/ion bonded to a number of ligands.