Alternative general definitions of ionicity and ionic radii based on the charge density null-flux concept are introduced. This method is local in nature and possible to adapt to any atom in any physical system including surfaces, interfaces, defects and alloys. These and other explicit advantages, as compared to the standard approaches, are discussed in detail. The current approach is especially suitable for density functional methods, and is applied to a number of III-V semiconductors, alkali halides and a few alkaline earth compounds. Good agreement with traditional results is found.