The periodic table has two new heavyweights, elements 114 and 116, according to a committee of international chemists and physicists.

The elements are fleeting — they are created by bombarding lighter elements together and exist for less than a second before undergoing radioactive decay.

Such a short lifespan means that we can't say much about them other than they really do exist.

"The lifetimes of these things have to be reasonably long so you can study the chemistry — meaning, pushing a minute," Paul Karol  of Carnegie Mellon University in Pittsburgh, who chaired the committee that approved the new elements, told New Scientist.

The evidence for element's existence has been mounting for more than a decade. In 1999, for example, Russian scientists with the Joint Institute for Nuclear Research bombarded plutonium-244 with calcium-48 to produce a single atom of 114, which has an atomic weight of 289.

Further collaboration between Russian and U.S. scientists at the Lawrence Livermore National Laboratory resulted in papers published in 2004 and 2006 on the creation of the elements 114, 116, and the yet-to-be-approved 118.

To create 116, the researchers smashed together curium atoms, which have 96 protons in their nucleui, with calcium nuclei, which have 20 protons. This lasted a few milliseconds before decaying into 114, which in turn decayed into copernicum, element 112.

These papers served as the basis for review by the International Union of Pure and Applied Chemistry, which made the formal announcement of the new elements on June 1 with the publication of a paper in Pure Applied Chemistry.

The elements currently go by the placeholder names ununquadium and unuhexium, which by IUPAC convention are derived from the digits 114 and 116.

The Russian discovery team at JINR has proposed flerovium for 114, after Soviet element finder Georgy Flyorov, and muscovium for 116, after Russia's Moscow region, according to Wired.

The committee also reviewed claims associated with elements 113, 115, and 118, but found they are not yet conclusive and thus do not meet the criteria for discovery.

For more information on how the elements were discovered and the review process, check out the video above from the University of Nottingham's Periodic Table of Videos series.

More stories on the periodic table: 

• Elemental shift: Periodic table gets weight changes 
• The world's smallest periodic table 
• Harry Potter and the Periodic Table 
• Heaviest element officially named Copernicium