Mendeleev's periodic table wasn't the first, but it won

Dmitri Mendeleev’s periodic table was presented to the Russian Chemical Society on 18 March 1869 (6 March in the Julian calendar Russia then used), but it was not the first periodic arrangement of the elements. It is the one that survived because Mendeleev left gaps for undiscovered elements and predicted what they would be like.

Mendeleev himself was absent. The best-documented account says he was ill, and his colleague Nikolai Menshutkin read the paper for him; the rival story, that he was away inspecting cheese cooperatives, can be traced back only to a 1974 article. His key claim, in his own words:

“If all the elements are arranged in the order of their atomic weights, a periodic repetition of properties is obtained.” — Dmitri Mendeleev

The rivals

• 1862: French geologist Alexandre Béguyer de Chancourtois wound the elements around a cylinder, his “telluric screw”.
• 1865: John Newlands proposed a Law of Octaves. The Chemical Society refused to publish it, and only in 1998 did the Royal Society of Chemistry put up a plaque calling him the discoverer of the periodic law.
• 1868: Lothar Meyer drew a table strikingly like Mendeleev’s, but it was not published until 1870.

Why Mendeleev’s won

He was willing to overrule the data. He swapped iodine and tellurium, defying their atomic weights so each sat with its chemical family; in 1913 Henry Moseley’s atomic numbers showed he was right. He also described five missing elements in detail, and three turned up: gallium (1875), scandium (1879) and germanium (1886). For “eka-aluminium” he forecast a density of about 6 g/cm³; gallium came in at 5.9.

He built the system when only about 60 elements were known. Today’s table holds 118, and element 101, mendelevium, carries his name.