Ununennium is an as-yet undiscovered element which is categorized as a transuranic element, meaning that it has an atomic number higher than that of uranium. Transuranic elements share a number of interesting traits which make them topics of intense study for scientists, and the discovery of ununennium would mark a major scientific breakthrough. Several attempts have been made to produce this element synthetically, although these attempts have proved unsuccessful as of 2008.
The thing that would make this element remarkable is that it would be the first element in the eighth period or row of the periodic table, marking a major event in the science world. Given the structure of the periodic table, the existence of ununennium can be fairly confidently predicted, and some scientists have also made speculations about the element's potential chemical properties.
Given its position on the periodic table, ununennium is probably going to be an alkaline earth metal. It may also turn out to be a liquid, which would make it the first radioactive liquid element, along with one of the few liquid elements. Like other transuranic elements, ununennium is probably extremely unstable, existing for only seconds at a time.
The instability of this element makes it unlikely to appear in nature. Therefore, scientists will have to produce it synthetically if they wish to observe it. Synthetic production of elements is usually accomplished by creating collisions of various isotopes of other elements in a linear accelerator. Depending on which isotopes are used, an new element may appear, albeit briefly, before it decays into the form of a more stable element. Typically only a few atoms of an element are produced at a time with this method, making observation very challenging, to say the least.
One might reasonably inquire about how this element could have a name, since it has not been discovered yet. Ununennium is named for its atomic number, 119, using a systematic element naming system developed by the International Union of Pure and Applied Chemistry. Several other elements which have not been discovered yet have also been named, so that scientists can discuss them using standardized language. If and when this element is successfully synthesized and observed, the laboratory which makes the discovery will have the honor of proposing a name; like other transuranic elements, ununennium will probably be named for a famous scientist or the location in which is is discovered.