Missing item would complete this alpha decay reaction? #"_98^251Cf# #-> ##"_96^247Cm + ?#

1 Answer
Sep 22, 2016

If you recall that conservation of mass dictates that the atomic number and mass number must add up on both sides to be equal, you should find that

#""_(2)^(4) X#

is missing. That means the mass number is #4# and the atomic number is #2#. That is the helium atom. More specifically, it is #""_2^4 "He"#, which is Helium-4.