Question

most atoms undergo nuclear decay is because

Answer 1

They are isotopes undergoing half-lives and they are radioactive.

Answer 2

Every atom will decay eventually according to modern physicists, entropy is always increasing in our universe.


Here is a source that discusses nuclear decay.

Answer 3

http://www.newton.dep.anl.gov/askasci/phy00/phy00774.htm

Answer 4

I think it answers your question rather well.