Atomos (ἄτομος) means "indivisible," "unable to be cut," and was the Greek philosophers' term for the smallest indivisible unit of matter — from which our modern word "atom" derives. In the New Testament (1 Corinthians 15:52), it appears in the phrase en atomō — "in a moment" or "in an indivisible instant" — to describe the speed at which the resurrection will occur at the last trumpet.
Paul reaches into the vocabulary of Greek philosophy — the language of Leucippus and Democritus who theorized that reality consisted of tiny indivisible particles — and presses it into eschatological service. "In a moment (atomō), in the twinkling of an eye, at the last trumpet — the dead will be raised imperishable." The resurrection is not a gradual process; it happens in the smallest conceivable unit of time. God does not need time to recreate what He originally created. The same God who spoke the universe into existence can transform mortal bodies into immortal ones instantaneously. The word atomos reminds us that resurrection is not natural evolution but divine fiat — as immediate and sovereign as the original creation itself.