Why are the larger elements more unstable and radioactive the closer to the bottom and right of the periodic table you go?

Question

Why are the larger elements more unstable and radioactive the closer to the bottom and right of the periodic table you go?

In: Chemistry

Answer 1

As you go down, and to a lesser extent from left to right, you’re going to elements with larger atomic weights. For radioactivity, you’d do better to look at all the isotopes. For instance, here:

https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html

As you can see there’s a thin line of stable isotopes, from hydrogen-1 to lead-208. On either side, there are radioactive ones, of shorter half-life as you move out.