In 2005, a Joint Working Party (JWP, formerly also called JWG) of independent experts drawn from IUPAC and the International Union of Pure and Applied Physics (IUPAP) was appointed by the presidents of these organizations to determine priority of claims to the discovery of new chemical elements. The JWP worked according to the criteria for the discovery of elements previously established by the 1991–1993 IUPAC/IUPAP Transfermium Working Group [1], [2], [3]. A summary of the current criteria and procedure was recently published in Chemistry International [4].

The JWP has earlier reported [5], [6], [7] on the discovery of elements with atomic numbers 112, 114, and 116. These elements were subsequently named copernicium, with symbol Cn [8]; livermorium, with symbol Lv; and flerovium, with symbol Fl; respectively [9].

The JWP reports on the claims of priority of discovery of elements with atomic numbers 113, 115, 117, and 118 were submitted in 2015; prior to publication, each of the claimant laboratories was asked to check the contents and findings in these drafts for technical accuracy. The reports were also reviewed by independent expert referees. Finally, the findings were accepted by the Division Committee of the IUPAC Division of Inorganic Chemistry (Division II) and by the Executive Committees of the two Unions. The reports were subsequently published in Pure and Applied Chemistry [10], [11]. Priorities for the claims of discovery were determined as follows.

The RIKEN collaboration, of Morita et al. [12], [13], [14], [15] has fulfilled the criteria [1], [2], [3] for element Z=113 [10].

The collaborating laboratories in Dubna, Livermore, and Oak Ridge coordinated by Oganessian, et al. [16], [17], [18], [19], [20] have fulfilled the criteria [1], [2], [3] for elements with Z=115 and 117 [10].

The results of the collaboration between the laboratories in Dubna and Livermore [21] have satisfied the criteria for discovery of element 118 [11].

The role of IUPAC is to provide a technical review of the names and symbols proposed by the discoverers. In early 2016, the recommendations for naming elements of 2002 [22] was revised to allow newly discovered elements belonging to the halogen and noble gas Groups to have appropriate endings [23]. Its main points are summarized here. In keeping with tradition, newly discovered elements can be named after:

• a mythological concept or character (including an astronomical object),

• a mineral, or similar substance,

• a place, or geographical region,

• a property of the element, or

• a scientist.

To avoid confusion in the literature, when a name has been used for a particular element, but a different name has ultimately been chosen for that element then the first name cannot be transferred for use for another element. The names of all new elements should have an ending that reflects and maintains historical and chemical consistency. This would be, in general, “-ium” for elements belonging to Groups 1–16, including lanthanoids and actinoids, “-ine” for elements of Group 17, and “-on” for elements of Group 18. Finally, we note from the IUPAC 2005 recommendations [24] that: “It is obviously desirable that the names used in any language resemble these names as closely as possible, but it is recognized that for elements named in the past there are often well-established and very different names in other languages”.

Following the acceptance of the claims, and in accordance with the procedures established by IUPAC for the naming of elements [23], whereby the discoverers are accorded the right to propose a name and a symbol, the discoverers at RIKEN Nishina Centre for Accelerator-Based Science (Japan), Joint Institute for Nuclear Research, Dubna (Russia), Oak Ridge National Laboratory (USA), and Lawrence Livermore National Laboratory (USA) were invited by IUPAC to propose names and symbols for the elements with atomic numbers 113 (RIKEN), 115 and 117 (Dubna, Livermore, Oak Ridge), and 118 (Dubna and Livermore). The outcomes of this process are as follows:

The Inorganic Chemistry Division Committee considered the proposals of the discoverers’ laboratories, and it recommended to the IUPAC Bureau and Council that the names nihonium, with the symbol Nh; moscovium, with the symbol Mc; tennessine, with the symbol Ts; and oganesson, with the symbol Og; be accepted for the elements with atomic numbers 113, 115, 117, and 118, respectively. These provisional recommendations of the names and symbols were made available for review and comment in May 2016. The final recommendations were approved by the IUPAC Bureau in November 2016, as authorized by the Council at its meeting in 2015. This final part of the process followed the statutory period during which the recommendations were open for public comment for a period of 5 months.

Finally, as serious claims associated with elements having Z=119 or above have not yet been made, we note that, for the first time, the Periodic Table exists with all elements named and no proposed or pending new additions. This, however, does not mean that the Periodic Table is complete, and a new JWP is being planned already by IUPAC and IUPAP.

Membership of the Inorganic Chemistry Division Committee for the period 2016–2017 is as follows: President: J. Reedijk (The Netherlands); Vice President: L. Öhrström (Sweden), Secretary: M. Leskela (Finland); Titular Members: L. Armelao (Italy), T. Ding (China), P. Karen (Norway), R. D. Loss (Australia) D. Rabinovich (USA), T. Walczyk (Singapore/Switzerland), M. Wieser (Canada); Associate Members: Y. Abdul Aziz (Malaysia), J. Colón (Puerto Rico), M. Drabik (Slovakia), L. Meesuk (Thailand), K. Sakai (Japan), N. Trendafilova (Bulgaria); National Representatives: J. Darkwa (South Africa), M. Diop (Senegal), L. Galamba-Correia (Portugal), M. Hasegawa (Japan), S. Kalmykov (Russia), A. Kiliç (Turkey), P. Knauth (France), G.J. Leigh (UK), S. Mathur (Germany), K.B. Yoon (South Korea).

We are indebted to the members of Division II, the Editorial Board of the Journal, the formal referees and the chemical, wider scientific, and public communities for their feedback on the provisional document. We thank all who responded for their interest, proposals for translations, and suggestions of alternative names, including the many thousands who signed specific petitions on the World Wide Web to name certain elements and several high school classes and students who came up with suggestions.