The periodic table has had a big year. It started with the IUPAC announcement in January 2016 that elements 113, 115, 117 and 118 have been added to the 7th row. The naming honour was given to the scientist or group of scientists who were credited with their synthesis. In June 2016, four names were proposed, and if there are no objections, these names will be official in November 2016.1 The provisional names followed the IUPAC guidelines.
Nihon is one of two ways to say “Japan” in Japanese, and literally means “the Land of Rising Sun”.
Honouring the Moscow Oblast, this region is home to the city of Dubna, the site of the Joint Institute for Nuclear Research. (Coat of arms pictured)
The ending is “ine” indicating it belongs to the halogen family
Since Og belongs to the Noble gases, it has an “on” ending. Yuri Oganessian (left)
Three of the four elements are named after places that are significant to their synthesis and the fourth is named after a Russian nuclear physicist.
These newly-named elements are more “synthesized” than discovered. Only 94 elements of the 118 have been discovered naturally on earth. The rest have been synthesized by speeding up nuclei using a particle accelerator and smashing them into heavier target nuclei — not as easy as it sounds. The challenge is not just making these elements but finding evidence of its brief existence. These superheavy elements are unstable — the nucleus has a massive positive charge. They quickly undergo decay — sometimes in a very small fraction of a second. Scientists can determine what was made by identifying the product of its decay and its decay chain. The difficulty is that the daughters of the decay can be hitherto unknown isotopes. In order to confirm the superheavy elements, these new isotopes also have to be unequivocally identified.
The RIKEN collaboration team in Japan was given credit for element-113, which they named nihonium. It was made by bombarding a bismuth target with zinc-70 nuclei. The half-life is 20 seconds, making it the longest lived of the new elements.2
The other three were achieved by a collaborative effort from the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, the Lawrence Livermore National Laboratory in California and several other institutions. For element 115, calcium-48 was accelerated to a high velocity in a cyclotron and directed at americium-243. This approach was also used with target elements of berkelium-249 to make element 117 and californium-249 to make element 118. All of these atoms quickly decay with the emission of alpha particles. The daughters of the decay also undergo alpha decay. The products of the alpha decay chain provide the evidence of these superheavy atoms.
Moscovium is named after Moscow Oblast where JINR is located. Oganesson honours Yuri Oganessian, a Russian physicist — still living; see article on “Signature Mugs: Texas connections”, pages 14-15 this issue. The name tennessine comes from the US state where Oak Ridge National Laboratory is located. Here they were able to produce and isolate enough of the rare berkelium to use as a target at JINR.
How does this impact the high school classroom other than making your classroom periodic table outdated? New discoveries are always a great discussion opportunity. Teachers can highlight the changes to one of chemistry’s most important tools and icons and the excellent example of collaboration of teams of scientists worldwide. It can also add some interesting context to the introduction of subatomic particles and isotopes. Some student questions are given at the end of this article as possible high school curriculum tie-ins. Sadly you will no longer be able to impress your students with your Latin to explain that “ununtrium” stands for 1-1-3. Those placeholders are now gone but there is still plenty of Latin to be found on the table.
You can have your students participate in our Design the newly-named elements contest for our Periodic Table Project — next page. This project fits nicely into the introduction of the atom or the periodic table. Consider passing on this project to junior science teachers or open the idea up to a science club or art class.
- How many protons and neutrons does calcium-48 have? If this isotope makes up only 0.187% of natural calcium by mole fraction, why do scientists choose it instead of the other isotopes of calcium?
- What is the atom that forms from a successful fusion collision of californium-249 atoms and calcium-48? During this fusion, three neutrons are lost. What is the mass of this atom?
- These new atoms undergo alpha decay (loss of helium-4). What is the daughter of an alpha decay of nihonium? Moscovium? Tennessine? Oganesson?
Photos: Moscow Oblast Coat of Arms (Hellerick, commons.wikimedia.org wikicommons);
Yuri Oganessian www.kremlin.ru