Can someone me i suck at chemistry.

15. the radioisotope radon-222 has a half-life of 3.8 days. how much of a 198.6 g sample of radon-222 would be left after approximately 23 days? (show your work)

16. how can an element be artificially transmuted? give an example that has an element and what it is transmuted into.

17. why does the mass and charge of an alpha particle make it less penetrating than a beta or gamma? discuss both the mass and the charge?