The "Electron Shell" by the current model takes up the most space due to its location in any given place along a series of orbits, but has the least mass.
The most space of an atom is vacuum.
The protrons and the neutrons take up the most space in a atom.The nucleus takes up the majority of the atoms mass but the majority of the atom at about 99.99% of the atom is actually empty space.
Technically, the term particle here is incorrect. The distinction must be made between particle (the things that make up elements and compounds) and sub-atomic particles. (the things that make up elements) In an atom, the sub-atomic particle occupying the most space is the nucleus, containing protons and almost always, neutrons. The rest of it is empty space, save for the orbiting electrons, which are quite tiny in comparison to the nucleus.
The electron cloud makes up most of the size of an atom. Electrons are found in regions around the nucleus, and their movement creates a cloud-like structure that extends far beyond the nucleus itself.
The electrons
A great, great amount of empty space. I refer you to the link attached.
The valence electrons are the part that takes place in a chemical reaction.
Only the valence electrons
In the nucleus.
oxygen
It’s the most massive part of the atom
In the nucleus of an atom, the positively charged particles are called Protons.