The only thing that can separate a compund is ?
In an atom the strong nuclear force keeps? :o :o :confused: :confused:

To separate 2 atoms bound together in a compound, you need to break the bonds between them, this requires ENERGY and I believe that is the answer for your first question. [im not 100% on the interpretation of the question though]

For your second question, I can help a little more as a physicist.

In the nucleus of an atom you have a dense cluster of protons and neutrons. The protons are all positively charged and the neutrons have no charge. This means that all of the protons should repel each other strongly and so a nucleus should not be stable. However it is! The strong force is a VERY strong force that acts only over a VERY short distance (over 100 Newtons at 1.3 femtometers) and dies off exponentially. Once protons get close enough together , the strong force overtakes the repulsion, and the protons come together into the nucleus.

Hope the second answer made up for lack of detail in the first one ;)