The coordination number is the number of ligands directly attached to the central metal ion in a coordination compound. These ligands can be ions, atoms, or molecules. The most common coordination number is 0, but it is also not rare to see 2 and 4 as coordination numbers.
a)-- There are four ligands bonded with a central metal ion, so the coordination number is 4. This compound consists of 2 ions ( and .
b) - There are six ligands bonded with a central metal ion, so the coordination number is 6. This compound consists of 4 ions (Cr 34 and ).
c) - There are two ligands bonded with a central metal ion, so the coordination number is 2. This compound consists of 6 ions and