Periodic Table

Search by exact atomic number or element symbol, or by part of an English or translated name. Case and diacritics are ignored for names. Exact symbols take precedence: Fe selects iron. The table keeps every element in place; nonmatches are dimmed. A search reveals its first match horizontally without opening details.

Tab enters the matching element buttons. Left/right move by atomic number, Home/End to the first/last match. Up/down choose the nearest column in the preceding/following displayed row. Enter or Space opens details; Close returns to the element. The 18-column layout displays all lanthanoids (57–71) and actinoids (89–103) in separate rows. These are series positions, not a decision about which members belong to group 3.

Standard atomic weights are dimensionless and shown here as approximate values from the existing local dataset. For elements without a standard atomic weight, brackets show an isotope mass number A selected in that dataset, without a unit. The selected isotope is not asserted to be the current longest-lived one. Thorium, protactinium and uranium do have standard atomic weights.

The legacy dataset supplies the other numeric properties, electron configurations, oxidation states and isotope entries. Its physical properties do not consistently distinguish measurement conditions from predictions; this tool does not label them all as measured values. No complete chemical-data audit or refresh has been performed. Missing values remain “Not provided”, and small nonzero values use scientific notation. Isotope half-lives are displayed only when supplied; positive abundance does not imply stability.

Search, selection and detail visibility are saved through the existing bounded state mechanism; element data are loaded separately. Search or selection restoration does not automatically move keyboard focus.

References for notation and layout conventions: IUPAC. Standard-atomic-weight versus mass-number classification: CIAAW. These references describe the presentation conventions, not the provenance of every legacy property value.