What it does
I'm not familiar with "Atomic Transmutation" as an official Magic: The Gathering keyword or ability. It doesn't correspond to any printed mechanic in the game that I can verify.
It's possible this is a custom or homebrew card mechanic, a misremembered name, or terminology specific to a particular playgroup or unofficial set. If you can share the exact card text or where you encountered it, I can help explain how it likely functions and how it would interact with Commander's rules.
If you meant a real mechanic—perhaps something like Transmute (a Dimir keyword that lets you discard a card and pay mana to tutor for a card with the same mana value), or transform/Disturb effects—let me know and I'll give you a proper rundown of what it does and the nuances people commonly miss.
Iconic cards with Atomic Transmutation
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