Sorry Josep; Atoms can decay. They can also anti decay.

The problem is twofold;

1. Since Bohr's groundbreaking work, it has been shown that orbits etc are arbitrary descriptors, more like analogies. (Spin being another analogy.) Trying to see the relevance of quantum mechanics in a non quantum scenario, (for instance, the universe we can observe) ultimately leads to confusion and gets you no further. hence anti decay is difficult to describe.

2. Sad but true, the giants on whose shoulders scientists stand have had their work refined and even totally contradicted. But to most of them, that would not be a problem. Einstein set the scene for and proved the rationale for quantum probability, and then spent the rest of his life regretting it as he had huge problems with the revelation this meant. Causing Bohr to tell him to stop telling God how to roll his dice! A couple of years later, Bohr's wonderful description of an atom looking like a solar system with orbiting electrons was shown to be inaccurate, but no matter, as a metaphor it works quite well.

An important point here that perhaps shows the difference between clinging to a theology and not doing.   If Bohr's thesis was a text that was to be accepted rather than challenged, it would 1) have the status of the bible and 2) stifle advancements as a result.

Newton's Principia was a holy grail for a couple of hundred years, but the central plank, that of a steady state with real time and distance lasted till Fred Hoyle died, and by then, the rest of the world had embraced the stunning concept of relativity in relation to the birth of time itself, or the big bang as it is known.

You see, that's the problem with most religions; they are not adventurous enough. The reality is far more wondrous, exciting, awe inspiring and HUGE...

By the way, I am a Pastafarian for two reasons; 1) the work I do these days for the government means they appear to have to know my religion and this is available under freedom of information, so couldn't resist it. 2) My in laws can no longer accuse me of not having faith. (Although I reckon they suspect me of taking the piss....)