"Languages are true analytical methods" -Antoine Lavoisier
A molecule is a conglomeration of atoms. A conglomeration of atoms is called a molecule. An arrangement of atoms must be "sufficiently stable" to form a molecule. A neon molecule, however, contains one atom. A molecule, of course, can be divided into "atomic volumes". Therefore, a molecule can be reduced.
But a cherry pie cut in half does not make the pie a cherry. A pie is an objective agreement of one gathering of substances. Just as a molecule is a gathering of atoms, or one atom.
In terms of logic, A equals B in its entirety. A molecule is a small unit of mass, thereby defined.
There again, one hour contains 60 minutes. An hour is 60 minutes. An hour can become 1/2 an hour and 1/4 of an hour and so on. But an hour does not become a minute. The passing of that hour relative to circumstances. So that 1/2 of a molecule does not make it an atom, but it reduces its mass.
Quantum chemistry attends to the particulars of molecules and atoms to make sense of the invisible. A certain sense of organization and familiarity with the invisible helps the chemist understand. In other words, a molecule could be called a "clump", instead of a molecule. Molecule in french means, "extremely minute particle". That particle has organization of some type and it makes sense within its environment and the sense which it makes is relative to another particle.
A molecule is proof that even at the most basic level of life, something is attempting to make sense. What if you went to the grocery store to buy cereal and instead of it being in a measured box, it was strewn among the onions? Wierd, right? So how wierd would it be for atoms to be strewn about without molecular structure? Without the appropriate chemical or electrical occurences which account for the structure?
In the interest of sane organization, which helps the world make a little sense, I say that molecules cannot be changed to atoms. Just as a baseball team cannot be changed to one player, though it can seem that way by persuasions of media.
In the case of the polar molecule, water, it is the atoms which make the molecule a molecule by not just the atoms but by positive charge on one side and negative on the other. There is a certain structure to a molecule and that structure in its entirety is called a molecule.
If this riddle does nothing else, it emphasizes the critical importance of language and the organization of definitions and how it allows for understanding beyond our immediate empirical experiences.