Why Is Radioactive Material Unstable (Except for Thorium)? By [Hydragyn] a student that love science When we talk about radioactive materials, the first thing that pops into most people’s minds is danger, glowing green ooze (thanks pop culture), and nuclear fallout. But scientifically, what makes these materials unstable? And why does thorium often get a pass in the conversation? Let’s break it down. --- The Basics of Radioactive Instability At the heart of every atom lies the nucleus, composed of protons and neutrons. The number of protons defines the element, but it's the ratio between protons and neutrons that determines stability. Most stable elements have a balanced ratio that allows nuclear forces (which hold the nucleus together) to overpower the repulsive force between protons. However, once you get to heavier elements—like uranium or plutonium—things get weird. The repulsion between the many protons becomes too strong for the nuclear force to hold everything together inde...