Most English speakers are flexible on where syllables get split, especially unstressed ones. Both a-tom and at-om sound fine to me. I could also see ay-tom in some North American dialects (if this seems ridiculous, ay-tomic is more mainstream, ay-tonal is standard).

My girlfriend's learning Turkish, and one of the customs that one says after being thanked for cooking a meal is "afiyet olsun". That is, "aff-ee-yet awl-soohn" with the relatively little stress on any particular part.

Her, being Italian, puts all the intonation at the beginning so it becomes "AFF-ee-yet AWL-soohn" and it just sounds like gibberish. Sometimes even if I know what she's trying to say, it still comes across as alien.

It's insane how intonation can completely change a language, and even a well defined language like German, a phonetic language just like Turkish, still sounds really bad if you don't get the intonation right (see: Trey Parkers attempts to speak German in South Park episodes)

And soon you learn that when it is an adjective it is a-tom-ic and not at-om-ic

The syllables are a-tom, but word breaking at the end of a line doesn't follow syllables in english.

The anatomy of an atom.

Tha'ts the thing: it is a-tom where I live