A Russian-American team working at the Joint Institute for Nuclear Research in Dubna, Russia, has created two new super-heavy elements, with atomic numbers 113 and 115. The team produced only four atoms of the short-lived new elements, enough to claim success but not enough for the finding to become official.
The results will have to be replicated at another laboratory before the new elements are added to the periodic table -- the chart that shows how different elements are related by their chemical characteristics.
Only 92 elements occur in nature, but physicists have produced 18 more that have been officially recognized and named. The Dubna team has also produced elements with atomic weights of 114, 116 and 118, but those experiments have not been replicated and the elements are not officially recognized. A Lawrence Berkeley National Laboratory team had also claimed creation of element 118, but the announcement was retracted when one researcher was shown to have fabricated data.
The atomic number refers to the number of protons in the nucleus of the atom, which is matched by the number of electrons orbiting the nucleus. The nucleus also contains many neutrons, which govern the element's stability. Americium-243, for example, is element 95; it has 95 protons in its nucleus and 148 neutrons.
The Dubna team bombarded a target of americium-243 with ions of calcium-49, which has 20 protons and 28 neutrons. When the two came together in the right configuration, they produced element 115, which survived for 90 milliseconds. It decayed by emitting an alpha particle (two protons and two neutrons) to become the new element 113. That, in turn, broke down to known elements 111 and 105, before fissioning into smaller nuclei.