See more at Wikipedia.org...

nm. atom, smallest part of an element (Physics, Chemistry); something that is extremely small, minute or microscopic object

n. atom, atomy, particle, speck

N F
atom| ultimate component of matter| particle incapable of being divided

(n.) = atom.
Ex: Thus atoms, mountains and men are things studied by discipline such as physics, geology and biology.
----
* átomo de hidrógeno = hydrogen atom.
* átomo de oxígeno = oxygen atom.
* átomo monovalente = monad.