Two new elements have been added to the periodic table after a three-year review by the governing bodies of chemistry and physics.
The elements are currently unnamed, but they are both highly radioactive and exist for less than a second before decaying into lighter atoms.
The table is the official compendium of known elements, organised according to properties of their atomic structure.
Details have been published in the journal Pure and Applied Chemistry.
The review was conducted by a joint working party of the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP).
In recent years, there have been several claims by laboratories for the discovery of new chemical elements at positions 113, 114, 115, 116 and 118 on the periodic table.
The working party concluded that elements 114 and 116 fulfilled criteria for official inclusion in the table. The others, as yet, do not.
The new elements have temporary titles of ununquadium and ununhexium, but final names have yet to be settled on.
The discovery of both elements has been credited to a collaborative team based at the Joint Institute for Nuclear Research in Dubna, Russia, and Lawrence Livermore National Laboratory in California, US.