Question

"(atom) -> (same atom) + gamma ray" the atom does not change. why?

1-how did it create such energy?

2-will the decay end?

3-how is it dangerous compared to other types of decay?

Answer 1

Gamma rays are just the effect of a nucleus rearranging itself into a lower energy state, much like tins of food stacked in a store collapsing into an untidy heap.

Explanation:

The nucleus didn't create the energy, it was left in a high energy state after some other (normally `alpha` or `beta`) decay.

The decay normally happens only once per nucleus (though there is a finite probability of emitting two lower energy gamma rays) so without further `alpha or beta` decays it will stop.

Gamma is relatively low risk because it isn't very ionising. The chances are it will just pass straight on through you (this isn't a recommendation to try it!) Certainly it is considered less harmful than alpha or beta particles.