Gurdjieff gives a definition of "atom" as the smallest amount of something that evinces all of its properties.

This is an information-theoretic view, and it allows us to speak of an "atom" of water, an "atom" of ice, and so on.

The property "alive" while not meaningless cannot be limited to a set of matter/energy configurations. There is no "atom" of life.

This would be moot except that you are alive. You are [part of] the life of the Universe. You can't actually fix a boundary between you and it. The Universe may not always have been alive, but when you became alive it did too.