On Dec. 30, 2015, the addition of elements was verified by the US-based International Union of Pure and Applied Chemistry (IUPAC).

President of the Inorganic Chemistry Division of IUPAC Jan Reedijk said, “The chemistry community is eager to see its most cherished table finally being completed down to the seventh row.”

The elements are currently known by temporary names based on the number of protons in the nuclei. The elements: ununtrium, ununpentium, ununspetium and ununoctioum are to be given a permanent name and a symbol by their discoverers.

Nuclear chemist at Carnegie Mellon University and chairman of the group that the evaluated the claim Paul J. Karol said, “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.”

Three out of four of the elements with atomic numbers 115, 117, and 118 were first identified over a decade ago by researchers at the Joint Institute for Nuclear Research in Russia and the Lawrence Livermore National Laboratory in California.

The other, with an atomic number 113, was distinguished in 2004 by the RIKEN Research Institute in Japan.

Lead researcher at Japan’s RIKEN group Kosuke Morita said, “For over seven years we continued to search for data conclusively identifying element 113, but we just never saw another event. I was not prepared to give up, however, as I believed that one day, if we persevered, luck would fall upon us again.”