# Why is caesium-137 more stable than caesium-134? Tags: nuclear-physics, radioactivity, isotopes - Score: 29 - Views: 5410 - Answers: 3 - Answered: yes - Asked by: Melanie Shebel (449 rep) - Asked: 2017-06-21 - Edited: 2024-04-25 - Site: physics ## Question Caesium-133 is stable. Caesium-134 and cesium-137 are radioactive isotopes of cesium with half-lives of 2.065 years and 30.17 years respectively. Why does cesium-137 have a longer half-life if it contains three more neutrons than caesium-134 and four more neutrons than stable cesium? It seems to me that cesium-134 would have a longer half-life given that it only contains one more neutron than stable cesium. ## Answers ### Answer by Jon Custer (score: 35 [ACCEPTED]) As noted in the comments, all of the various Cs isotopes I'll mention decay by emitting a beta, converting the Cs isotope to a Ba isotope. Now, while details of nuclear decays are not necessarily touched on unless you are in a nuclear physics course, they are at least somewhat analogous to electron or photon decays. What I mean by that is that you are, at a hand-waving level, looking at an initial state (the Cs), final states (Ba in various possible energy lev