All radioactive sources have a half-life. Which statement about the half-life of a source is correct?

A. It is half the time it takes for an atom to decay

B. It is half the time for the radioactive source to become safe

C. It is the time it takes the actity of the source to decrease by half

D. It is half the time it takes the activity of the source to decrease to zero

You are attempting to recrystallize a crude product mixture. you add the appropriate amount of hot solvent and are allowing the solution to slowly cool to room temperature. however, at room temperature no crystals have appeared, which of the following methods should be used to induce crystallization? choose all correct answers. a) place the flask in an ice bath. b) swirl the contents of the flask. c) add a small seed crystal of the desired product. d) scratch the inside of the glassware using a stir rod. it can be multiple choices