As above really
no, particles get created and destroyed all the time, but I do have to say I'm not really clear on what you mean by atomic particles. Do you mean only those that make up atoms? If so do you mean, for example protons and neutrons but not their quarks? What exactly DO you mean. I assume you are leaving out photons for some reason.
I mean what I say, 'the stuff' the smallest stuff we know, I am not sure what that is nowadays but smaller than an atom.
What is the smallest stuff produced in particle accelerators?
But whatever it be, be it energy or matter or matter-energy, if you like, everything must have an ultimate age even if it was once something else.
More basically was all the stuff created at the same time?
Or did it take a while?
This "stuff" you mention requires an explanation of what it is. The smallest physical objects are all subatomic particles such as electrons, quarks, etc. These can all be created from and turned into different forms of energy. Energy itself is not a physical substance, but an abstract quantity. Any change or transfer in energy has accompanying mass with it. Both mass and energy are always conserved.
So, what is this "stuff"? Mass, energy, something else? The only answer I can possibly give is that I don't know. An easy answer would be that everything is 13+ billion years old, but it depends on how we define this "stuff".
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