Q. State the law of conservation of electric charges?
The entirety charge in an isolated system always remains constant. For instance Uranium (92U238) can decay by emitting an alpha particle (2He4 nucleus) and transforming tothorium (90Th234).
92U238 ----→ 90Th234 + 2He4
Total charge previous to decay = +92e total charge after decay = 90e + 2e. Therefore the total charge is conserved. That is it remains constant.