On 30th December 2015, the periodic table’s seventh row was finally completed by the addition of four new elements, numbers 113, 115, 117 and 118.
Uranium (element 92) is the heaviest element found in nature. All elements heavier than this are unstable and have to be synthesised. The four new elements are all highly unstable and superheavy (they have more than 104 protons in their nuclei), and exist for only a fraction of a second. This means that they can only be detected by measuring the radiation they produce during their decay. The new elements were first created in 2000 by bombarding heavy metal targets with beams of ions in a heavy-ion accelerator. The teams which synthesised the elements previously spent years gathering enough evidence for their existence.
Elements 113 and 115 are thought to be metals, while 117 may be a metalloid and 118 may be a noble gas. It is hard to know for sure since each element exists for such a short amount of time and so few have been created. Element 113 is currently known as ununtrium, and was discovered by a Japanese team called Kosuke Morita’s group at the Riken Institute. This is the first team in Asia to discover a new element, who created ununtrium by firing a beam of zinc-70 at bismuth-209. Elements 115 and 117 are currently called ununpentium and ununseptium and were discovered by a collaboration of three research groups; the Lawrence Livermore National Laboratory in the US, the Joint Institute for Nuclear Research in Russia, and Oak Ridge National Laboratory in the US. Element 118, called ununoctium, was discovered in 2006 by the Lawrence Livermore-Joint Institute for Nuclear Research in California.
Now that all four of these elements have enough evidence to support their claims, they can be added to the periodic table. This is the first time this has happened since elements 114 and 116 were confirmed in 2011. The teams have since been invited to name their confirmed elements. Element names can be incredibly creative, they can be named after a mythical concept, a mineral, a country, a property or a scientist. The associated symbol has to be completely unique and not be used for any other element, molecule or material. After IUPAC (the International Union of Pure and Applied Chemistry) accepts the suggested names and symbols, they will be under public review for five months, before the name is decided.
Now the elements beyond the seventh row of the periodic table can be focused on. For these to be created, the material being bombarded by ions has to be superheavy (and therefore have a short lifetime) itself. Synthesising enough superheavy material would take years. Synthesis of heavier elements may also require more advanced technology than is currently available. To create elements like these four, 1012 ions hit the target material per second. Any more than this could burn the target at the detector. A new Superheavy Element Factory is currently being built in Russia, which will have improved detectors that can measure much faster radioactive decays. Some researchers believe that some stable elements may exist beyond element 118, but so far no elements with more than 118 protons have yet been discovered.
Superheavy elements have little use in the real world due to their short lifetimes, however studying and attempting to create them can improve scientists’ knowledge of how the nucleus of an atom is formed, and thus the existence of matter.