Answer:
1. True - They are members of the same element - cesium, but they have different masses because they are different isotopes
2. True - They have different masses which mean they are isotopes of cesium
3. Not too sure - maybe stick with false
4. True - Both are members of cesium so they have the same number of protons, masses are different because of less/more neutrons
5. False - Both contain the same number of protons, but different number of nuetrons, hence the mass is different
6. False - False the mass number is different from the number of nuetrons - mass number equals no. of protons + neutrons
7. True - 134 + 3 = 137
8. False - both isotopes are radioactive. The biggest isotope is not the only isotope that is radioactive