There are 13 instances on the periodic table where the atomic mass does not increase along with atomic number. For each of these
13 instances, please provide the atomic number, name, and mass number of each pair of elements. For example: 18-Argon-40; 19-Potassium-39. Use the back if necessary.
I think a good strategy for these kind of problems is to just choose the atom with the highest mass number. At any rate, the answer actually is (and I guessed it as) (2) Francium-220. It has a half life of about 30 seconds.
