1. There are 20.3 g of (198 superscript)Au left after 13.5 days. If the half-life is 2.10 days, how many grams were in the original sample?
2. Calculate the atomic mass for the element Iron if there are two isotopes: (55 superscript)Fe, with a mass of 54.974 and 15% abundance. (56 superscript)Fe has a mass of 56.988 and 85% abundance.
3. A 75 g sample of (16 superscript)N decays to 9.4 g in 34.8 seconds. What is the half-life of (16 superscript)N?
4. Write balanced nuclear equations for each of the following processes.
a. (214 superscript and 82 subscript)Pb decays by alpha particle
b. (42 superscript)K decays by beta particle

i'm having trouble with chemistry and i would like some answers for these problems. explanations would be nice, too