why do soaps not work under hard water

The Ca²⁺ and Mg²⁺ ions in hard water form scum with soap. Thus they don''t form lather and thus don''t clean the dirt.

BEACAUSE HARD CONTAIN CA+2 AND MG+2 IONS,GIVE MEFNASIUM AND CALCIUM FATTY ACIDS  ,SO WATER DOES NOT REACT THOSE IONS SO SOAPS DOT WORK IN HARD WATER ,