The stable nuclei of lead are Pb-204, Pb-206, Pb-207, and Pb-208, what methods of radioactive decay would Pb-200 be likely to undergo. (Hint: chose all methods that would move the isotope closer to the line of stability.)

law of conservation of matter

i dont know the answe

it is the minimum amount of material needed to sustain a fission reaction.

critical mass is the minimum amount of fissionable material that must be assembled for a sustained fission reaction to take place. although two to three neutrons are produced for every fission, not all of these neutrons are available for continuing the fission reaction. if the conditions are such that the neutrons are lost at a faster rate than they are formed by fission, the chain reaction will not be self-sustaining.   at the point where the chain reaction can become self-sustaining, this is referred to as critical mass.