Pl hel The half-life of a radioactive isotope is 2.4 minutes. If you started with 100.0 grams, how many grams would be left after 7.2 minutes has elapsed? Explain how you arrived at your answer.

4al + 3o2 → 2al2o3 what does the "3" in front of o2 stand for? a) it indicates that there are 5 oxygen atoms after you add the coefficient and the subscript. b) it indicates that that there are are total of 6 oxygen atoms all bonded together as a single molecule. c) it indicates that there are 3 oxygen molecules chemically bonded to each other in the reaction. d) it indicates that there are 3 separate oxygen molecules in the reaction.