I'm not sure if this is a silly question, but I was sitting here with a cup full of cheezey poof balls thinking, "My goodness, it's like an amazing cheesey delicious liquid - huge water molecules!"
Of course my next thought was, "Wait a minute - water has two hydrogen atoms bonded to an oxygen, so that's not quite right. They wouldn't be round like this."
Then I started thinking about the diagrams we see in chemistry textbooks, etc., and how the atoms are always pictured as round balls. How do we know this is accurate? Is it possible for the atoms to be configured in more complicated shapes (e.g. not solid, crystalline, some type of lattice)?
It depends how you define the surface of an atom, atoms have no surfaces have only regions of space where you have more chances to find electrons. So in fact it is not right saying that they have a true shape at all.
Shapes of Atomic Orbitals
However if you plot the regions where you have the higher probability of finding electron of an atom you can obtain something like this:
These are the shapes of the first five atomic orbitals: 1s, 2s, 2px, 2py, and 2pz from Wikipedia. 1s orbital is sphere shaped but others orbitals have more complex shapes so atoms with many electrons have orbitals very different from a sphere.
Shapes of Molecular Orbitals
Molecules have more electrons and so even more orbitals. They can have very strange "shapes". I've calculated for you with GAMESS and Avogadro the LUMO $2b_2$ water's orbital that is one of molecular orbitals of water. This is the result:
Shapes of Atomic Constituents
For answering your question in the comment in fact even protons, neutrons and electrons don't have a real shape due to the wave-particle duality. However we can assume in many cases that neutrons are particles (so we suppose a spherical symmetry) but the de Broglie hypothesis state that they have also a wavelength!Tweet