What kind of particles are you talking about?

In between the subatomic particles is empty space.  So between the electrons and the nucleus is well, nothing.  It's an absence of matter.

Not completely true. The electrons and the protons on the nucleus do have an electromagnetic interaction. This interaction is due to exchanging photons and this is what you can find in between this dead space.

Yeah, but here's where you can question whether those photons are particles with mass or if they are just em waves.  This is where the concepts get really twisted and make my brain cry.  I'm going to go shiver alone in the corner now.