What is the coordination number and how does it relate to the number of ligands?

The coordination number is the number of ligands surrounding a central metal ion.

In coordination compounds, a central metal ion is surrounded by ligands, which are molecules or ions that donate electrons to the metal ion. The coordination number is the number of ligands directly bonded to the metal ion. For example, in a complex with a coordination number of 4, there are four ligands directly bonded to the central metal ion.

The coordination number is determined by the size of the metal ion and the size of the ligands. Larger metal ions can accommodate more ligands, resulting in a higher coordination number. Similarly, smaller ligands can fit more closely around the metal ion, allowing for a higher coordination number.

The coordination number can also be affected by the charge of the metal ion and the charge of the ligands. For example, a metal ion with a 2+ charge can accommodate more negatively charged ligands than positively charged ligands.

In summary, the coordination number is the number of ligands directly bonded to a central metal ion in a coordination compound. It is determined by the size of the metal ion and ligands, as well as their charges.