3. If the half-life model decayed perfectly, how many atoms would be remaining (not decayed) after 12 seconds?
(started with 200 atoms before decay). pls help :)

The characteristic of two different types of reactions are shown below. reaction a: electrons are gained by the atoms of an element. reaction b: protons are lost by the atom of and element. which statement is true about the atoms of the elements that participate in the two reactions? a: their identity changes in both reaction a and b. b: their identity changes in reaction a but not b. c: their identity changes in reaction b but not a. d: their identity remains the same.