Why does the half life of different elements differ?

Answer 1

Half-lives are different for each nuclide, not just each element, because of complicated theoretical considerations that are really beyond the scope of what we can answer here. Try taking some university courses in nuclear engineering and you might begin to get a glimmer of it.

At its most basic, it has to do with energy levels of nuclei with different numbers of nucleons. Some have lower energy and some have higher. The ones with higher energy are less stable.

Answer 2

The half-life of an element depends on its inherent stability and the balance between its nuclear forces. Elements with unstable nuclei undergo radioactive decay at different rates, leading to varying half-lives. Factors like the number of protons and neutrons in the nucleus, as well as the specific type of radioactive decay involved, contribute to this variation.