An ion is a specie that have no unpaired electron and is charged, either positively or negatively i.e. may be a cation or an anion. It is formed due to heterolysis of a molecule e.g HCl----> H+ + Cl-

A radical is a neutral specie having atleast one unpaired electron and is formed due to homolysis of a molecule e.g

H-H -------> H* + H*

The * shows an unpaired electron. Similarly CH3* is a radical.