Are atoms compressible? Liquids are not compressible, but what does compressible mean? Does it mean the increase in the density or decrease in volume? Or something else? Why are liquids incompressible, in a way nothing should be compressible because atoms are compressible, right? Is there a maximum density an object can acquire?
 A: Ever seen a spring? They are everywhere.
What kind of material would you consider incompressible? Steel?
If you put a force on it (called "stress"), it will be squeezed by a certain amount (called "strain").
The ratio of the two is called "elastic modulus" (if you like big words).
In fact, if you have a rod of that material, and tap one end of it, sound travels from one end to the other, in the form of a wave of compression, which is nothing more than spring behavior.
So the idea that atoms are incompressible is not so.
They may be really stiff, compared to us jelly blobs, but they are compressible.
A: "Compressible" means "decreases in volume under applied pressure."  But "pressure" is by definition a macroscopic, thermodynamic property that is found by averaging over gigantic numbers of microscopic collisions.  It therefore doesn't make sense to talk about the "pressure" exerted on a single atom.  The "volume" of an atom is also not clearly defined due to the quantum-mechanical uncertainty at those scales.  So the "compressibility" of a single atom is not a well-defined concept.
A: Atoms themselves cannot be compressed in general.


*

*Liquids are not very compressible (they are compressible) because of distances between atoms. Gases have the most distance
between atoms. Liquids have very little space in-between atoms, so when you press on them, the  their is not much more room to budge. Solids can budge because of there crystal structures.

*Nothing is infinitely incompressible.

*Infinite: black holes can have infinite density.
