Four new elements have been added to the standard periodic table and their creators from Japan, Russia and the United States will now come up with permanent names and symbols for them.

The International Union of Pure and Applied Chemistry (IUPAC) announced that atomic numbers 113, 115, 117 and 118 had been added to the list. This now completes the 7th period of the periodic table of elements.

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“The chemistry community is eager to see its most cherished table finally being completed down to the seventh row,” Jan Reedijk, president of the Inorganic Chemistry Division of the IUPAC, said in a statement.  “IUPAC has now initiated the process of formalizing names and symbols for these elements temporarily named ununtrium, ununpentium, ununseptium and ununoctium.”

The research into these elements dates as far back as 2004 and among the challenges was the fact they don’t hang around that long – in many cases just nanoseconds.

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“A particular difficulty in establishing these new elements is that they decay into hitherto unknown isotopes of slightly lighter elements that also need to be unequivocally identified,” Paul Karol, of the IUPAC’s Joint Working Party, said in a statement.

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These super-heavy elements, which include all the elements beyond atomic number 104, are not found naturally on Earth, and thus have to be created synthetically within a laboratory, according to LiveScience. Uranium, which has 92 protons, is the heaviest element commonly found in nature, but scientists are able to artificially create heavier elements by adding protons into an atomic nucleus through nuclear fusion reactions.

Among the goals in creating these heavier elements is the hope of discovering just how large atoms can be.