As both chlorine and sulfur throw their electrons such that they achieve their stable electrons to be the so called " modal atom " Therefore chlorine have to throw 1 electron to form 8 and sulfur have to throw 2 to form 8 . Therefore if they throw it will be negative while if they add it will be positive .
* Remember ( All Atmos have electronic figuration of most 2,8 or 2,8,8,8 )