Periodic Table of Elements - IUPAC | International Union of Pure and Applied Chemistry

IUPAC Periodic Table and Element Governance

• Latest Data: The current Periodic Table (released 4 May 2022) incorporates the "Standard Atomic Weights 2021" from the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW).
• Atomic Weight Notation: For elements lacking natural terrestrial isotopic abundance, the mass number of the nuclide with the longest confirmed half-life is provided in square brackets.
• IUPAC’s Core Responsibilities:
  • Establishing criteria for the discovery of new elements.
  • Defining temporary names and symbols for new elements.
  • Validating discovery claims and assigning priority (often in collaboration with IUPAP).
  • Coordinating the formal naming process, including a 5-month public review period.
  • Setting nomenclature rules for new elements.
  • Defining group structures (1–18) and collective names (e.g., lanthanoids, actinoids).
  • Periodically reviewing standard atomic weights and isotopic compositions.
• Group 3 Debate: IUPAC is currently working to resolve the composition of Group 3, specifically whether it should contain (Sc, Y, Lu, Lr) or (Sc, Y, La, Ac).
• Terminology Standards:
  • Groups: Recommended numbering is 1 through 18.
  • Collective Names: "Lanthanoids" (La–Lu) is preferred over "lanthanide"; "Actinoids" (Ac–Lr) is the standard term.
• Historical Context: The CIAAW has been active since 1899 and currently operates under the IUPAC Inorganic Chemistry Division.
• Resources: IUPAC provides the table in various formats (PDF) and maintains an interactive version at iupac.org/isotopes-matter. Detailed technical reports and recommendations are published in the journal Pure and Applied Chemistry (PAC) and the magazine Chemistry International (CI).