[thewax]

I tried researching this on the web but it gave too much details and wikipedia didn't really go into my question. I was wondering about why springs, on an atomic/molecular level, are elastic in that when they are compressed, they push with a force to attain the former state of equilibrium and when they are pulled out, they exert a force to pull the spring back into its former state of equilibrium.

[Tin Man]

There are a few different answers, and most of them don't pertain exclusively to chemistry. You're going to need to delve into physics a bit.

The first thing you can do is research Newton's laws. This will explain why things push and pull in response to a force, especially in the case of tension (like in a spring).

The next thing you can research is the idea of entropy, which is basically the idea that things will naturally move to a state of being more disordered, whether it be two substances mixing or air particles dispersing in a room.

Finally, understand that, physically, every substance I know of is compressed when pushed against, which is Newton's laws are valid. Even your table, even concrete is elastic to a certain degree. Some substances are, due to the forces acting on them, more elastic than others. The elasticity of an object has to do with many variables, including the types of bonds being used to hold the material together, the energy of the substance (heat makes things "softer), the thickness of a substance (which affects the amount of force it can withstand before bending), and so forth.

Hopefully this will give you a better direction with which to conduct your research, but at least know that the reason you aren't getting simple answers is because there isn't a simple answer, nor a single answer. 

[renge ishyo]

Tin Man's answer was great and surely deserving of his first mole snack  It may seem like an easy question, but actually to answer this question in a satisfying way requires many many years of work (perhaps even grad school!). Nevertheless, I'll add a bit of an idealized qualitative description for you if it helps any.

Imagine zooming in on an object to have a look at things on the atomic level; say, imagine zooming in on a solid cubic box. On the surface of the box what would you see? Electrons. The outside of the box would be covered with electrons that in an ideal sense would all be evenly spaced apart from one another so as to spread the electrons out across the atoms on the surface of the box like a uniform coat of paint. The same thing would happen for the atoms within the box so that the electrons inside are as far away as they can get from one another to minimize electron-electron charge repulsion.

Now consider bringing your hand closer and closer to push against the surface of the box. Your hand is made up out of atoms as well and as a result the surface of your hand is also coated with electrons trying to spread themselves out as far away from each other as possible. When you bring your hand really close to the box the electrons on your hand repel the electrons on the surface of the box causing them to push inward on the electrons just below the surface. The closer you get, the stronger the repulsion as more and more electrons just under the surface are compressed and add together their great repulsive strength to resist the hand's intrusion.  The surface electrons in turn try to resist being pushed inward and push back out on the hand. This is a qualitative description of Newton's third law. If you now remove your hand, the electrons that were being pushed inward are free to "rebound" to the surface into their most stable arrangement aided by the repulsion of the interior electrons. This is elastic rebound from compression.

The same general logic can be applied to elastic rebound for stretching. Say you take a material and pull on both sides so that the middle of the material is stretched. Since the atoms in the middle are being pulled away from one another there is more room for atoms and electrons there than there was before. These atoms try to fill the void and move in to the central area from the outer areas where the density of atoms (and therefore, electrons) is greater. In doing so they try to restore the object to its original form and "resist" your attempt to separate the two sides. If you suddenly release the material, there is a a frantic push and pull while the atoms readjust their densities throughout the material so that an even distribution is again reached.

There are other aspects to consider for elastic recoil on "real objects" which considers the nature of the bonding arrangement in the material, how far apart each atom was originally before you stretched or compressed, the entropic effects of the stretched vs. compressed state, etc. that are not taken into consideration in the simplified model described above.