Question

Why is Ra-226 is more radioactive than U- 238? "Radioactive decay" states an unstable nucleus (U- 238) forms a more stable nucleus (Ra- 226) by the release of high energy particles and radiation?

Answer 1

Here is my reasoning.

Explanation:

`""^226"Ra"` IS more stable than `""^238"U"`.

The binding energy of `""^226"Ra"` is 7.66 MeV/nucleon, while the binding energy of `""^238"U"` is only 7.57 MeV/nucleon. Thus, `""^226"Ra"` is more stable.

Don't confuse the rate of a reaction with the relative stability of the reactants and products.

For example, graphite is more stable than diamond, but the conversion of diamond to graphite is extremely slow because of a high activation energy.

In the same way, there is an "activation energy" for the escape of a particle from the nucleus.

The activation energy for `""^238"U"` decay must be much higher than that for `""^226"Ra"` decay.

If there were no activation energy, every atom would start decaying from the moment it was formed.

It seems quite unlikely that, instead of an activation energy, some sort of delay mechanism is built into each nucleus.