What is Co-ordination sphere?

Explanation

(i) The complex ion of the coordination compound containing the central metal atom/ion and the ligands attached to it . Is collectively called coordination sphere and are usually enclosed in square brackets with the net charge.
(ii) The other ionisable ions ,are written outside the brackets are called counter ions For example ,the coordination compound ` K_4[Fe(CN)_6]^(4-) ` and is referred as the coordination sphere
(iii) The other associated ion ` K^(+) ` is called the counter ion.