[Bliz2006]

What causes an atom to be a radioisotope?

What is the nuclear equation for the alpha decay of Gold-207? beta decay of Bismuth-210? positron decay of Carbon-11? electron capture by Radium-226?

Which is more stable: Carbon-14 or Nitrogen-15? Which would decay faster?

[Will]

Hope you find these links useful  :
http://www.chemicalforums.com/index.php?topic=59.0
http://en.wikipedia.org/wiki/Radioisotope
http://en.wikipedia.org/wiki/Alpha_decay
http://en.wikipedia.org/wiki/Beta_decay
http://en.wikipedia.org/wiki/Positron_emission
http://en.wikipedia.org/wiki/Electron_capture
http://en.wikipedia.org/wiki/Carbon-14
http://en.wikipedia.org/wiki/Nitrogen-15

[AWK]

http://www.chem.duke.edu/~jds/cruise_chem/nuclear/stability.html
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/shell.html
http://cwx.prenhall.com/bookbind/pubbooks/blb/chapter21/medialib/blb2102.html
http://www.plus2physics.com/nucleus_and_radioactivity/study_material.asp?chapter=1&page=3