What would happen if all the periodic table elements got together at once?

No, no. They don't form anything like the Hulk, and definitely won’t form a super-molecule containing one of everything.

There are two methods of putting it to the test, neither of which are practical.

The first method would require energy equivalent to dozens of Large Hadron Colliders-an impressive and extremely treacherous experiment indeed. The second method would be putting together a chunk of each element and observe what happens.

Both, however, would eventually create carbon monoxide and a pile of rust and salts rather than a cool Frankenstein element.

Image: blackchristiannews.com

Atoms are made up of a nucleus of neutrons and protons with a set number of electrons circling around them. Molecules form when atoms’ electron orbitals overlap and effectively hold the atoms together. What you get when you mix all your atoms will be influenced by what’s close to what.
Oxygen, for example, is very reactive, and if it is closest to hydrogen, it will make hydroxide. If it is nearest to carbon, it will make carbon monoxide. Certain elements, such as the noble gases, wouldn’t react with anything.
Bombarding the atoms together at 99.999 % the speed of light in the Large Hadron Collider might be able to break protons, but it could also be used to fuse a few nuclei together. But still it won't produce anything supernatural-and if there's any, it would probably decay into something more common in a fraction of a second. Moreover, you would need 118 colliders-one to accelerate each element in the Periodic Table to get the task done, which sounds pretty quixotic to me.

Image: scienceblogs.com

Another approach would be to toss a pulverized chunk of each element or a puff of each gas into a sealed container and observe the consequence. No one has ever tried this experiment either, but here’s how scientists think things would play out: The oxygen gas would react with alkaline metal (lithium or sodium) and ignite, raising the temperature in the container to the point that even Devil himself would complain. There are roughly 25 radioactive elements, and they would make your flaming stew a little dangerous. Flaming plutonium is a very bad thing-inhaling airborne radioactive material can cause rapid death.
Once temperature drops, the result would be as boring as the atoms-only scenario. Carbon and oxygen would yield carbon monoxide and carbon dioxide. Nitrogen gas is very stable, and would remain as is. The noble gases wouldn’t react, nor would a few of the metals, like gold and platinum, which are mostly found in their pure forms. The things that do react will form rust and salts. 



Some smaller level reactions can be shown here with cool videos. Take water and sodium. Two things we have at home, maybe even on the dinner table. Sodium in its elemental form is highly reactive to water.




Check out this video: Sodium v Water (slow motion) - Periodic Table of Videos

 Zinc and sulfer another another fantastic combo.   Zinc and Sulfur - Periodic Table of Videos 
Of course not just sodium reacts with water.  So does potassium.  

REFERENCES:
info: http://www.popsci.com/science/article/2010-10/fyi-what-would-happen-if-every-element-periodic-table-came-contact-simultaneously