So far we have identified ~118 chemical elements (four of them are still not officially recognized). Only the first 98 are known to occur naturally on earth, the rest have been made synthetically. About 32 of them occur on earth as pure elements, and the rest occur in combinations in compounds. Only 80 of the elements are stable. (An unstable element undergoes radioactive decay to form a lighter, stable element). The largest elements are created by smashing two smaller elements together at extremely high energies by using a particle accelerator. The resulting new elements are typically very unstable (decay within seconds) and we can only identify them by what they break into. They instabilities are not due to being on earth, but are due to the fundamental forces within the atoms. There is a theory that some super heavy elements (lots of neutrons compared to protons) will be relatively stable, so those may be found somewhere in the universe, but it is probably unlikely.

Actually, there are as many elements on Earth as there are in the Universe. There are 118 that we have found, though anything over atomic number 100 doesn't last for more than a couple milliseconds at most. Interestingly, anything on the periodic table with a higher atomic number than lead (Pb) is unstable and will eventually undergo radioactive decay.

There are 114 known elements in the known universe. A majority of the universe is made of the gases hydrogen and helium. The two most recent elements, Flerovium and Livermorium were added to the periodic table May 31, 2012; they are synthetically made (or man-made), and only last a few seconds.

Interesting question. There are nearly 120 elements that are known in the laboratory, with more being added periodically, but the very heaviest elements are so radioactive and have such short half-lives that I don't think they've ever been found in nature. Heavy elements in nature are formed in the cores of massive stars during supernovae, which are incredibly violent events that cannot begin to be replicated in the laboratory, so I'm pretty sure we don't know what the heaviest atoms that sometimes get formed in supernovae are, only that they don't last long enough for us to ever see them.

According to the wikipedia article, the heaviest element so far found in nature is element 98, Californium, which is created from the radioactive decay of other things. Plutonium, element 94, is the heaviest element that has ever been found that has not been the product of radioactive decay (and yes, lower- numbered elements can decay into higher-numbers by spitting out electrons. This happens because the decaying atom has more neutrons than is stable, and one of the neutrons becomes a proton and an electron, the latter of which is ejected).