References 485% CONFIDENCEOverall confidence: 85%How well the pin's source and references back up its dates.Weighted average of how firmly 4 references, the source included, support the pin's start and end times; a reference counts half as much for every 180 days older than the newestShow all pins at 75% confidence or better
The first entry is always the pin's source. Overall confidence is a weighted average of how firmly each reference supports the start and end times used above; a reference counts half as much for every 180 days older than the newest.
- [1]90%iupac.org/what-we-do/periodic-table-of-elementsiupac.org· Posted Sep 22, 2026· Starts Mar 6, 1869 ✓· 25% of score
Wikipedia's[2][3] Dmitri Mendeleev article states it plainly: "On 6 March 1869, he made a formal presentation to the Russian Chemical Society, titled The Dependence between the Properties of the Atomic Weights of the Elements". Russia was still on the Julian calendar, so contemporary Russian sources date the work to February; the manuscript sheet on Commons is signed 17.02.1869, the Julian date for 1 March, and the pin uses the Gregorian date Wikipedia gives for the presentation itself.
- [2]90%Dmitri Mendeleeven.wikipedia.org· Added Sep 22, 2026· 25% of score
Carries the date and the title of the presentation to the Russian Chemical Society, and the description of a table ordered by atomic weight and valence.[1]
- [3]85%Periodic tableen.wikipedia.org· Added Sep 22, 2026· 25% of score
Sets the 1869 table in context - "The first periodic table to become generally accepted was that of the Russian chemist Dmitri Mendeleev in 1869" - and records the Julian dates around it (17 February 1869, 1 March in the Gregorian calendar) and the printed table appearing in May 1869.[1]
- [4]75%Periodic Table - Royal Society of Chemistryrsc.org· Added Sep 22, 2026· 25% of score
The RSC's interactive table, for the modern form of what Mendeleev proposed; institutional context, not a source for the date.
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