In correlational research the effect that one variable has on the other is studied without the addition of any external factor by the researcher. The subject is studied in a natural environment.
In experimental research how and why one variable affects another variable is studied. The subject is studied in the presence of various different variables introduced by the researcher.
The particles in the atom's nucleus bond together because there is a strong nuclear force between the protons and neutrons that attracts them to each other and binds together the nucleus.
