Mendeleev's 1869 periodic table. Animation of the 1869 periodic table of the chemical elements, as published by Russian chemist Dmitry Ivanovich Mendeleev (1834-1907), showing its evolution into the modern periodic table. Mendeleev worked on organising trends in atomic weights and valency. From this, he developed the first true periodic table of the elements (final version published in 1871). The 1869 version of the periodic table was arranged vertically, instead of horizontally, and had several gaps and uncertainties. The animation shows the vertical lists being rearranged into horizontal periods, and then flipped left-to-right, and finally some elements moved from right to left. The animation then highlights the four missing elements. The gap at atomic weight 45 was filled by scandium (1879), at atomic weight 68 by gallium (1875), at atomic weight 70 by germanium (1886), and at atomic weight 180 by hafnium (1923). The animation then fades into a view of the modern periodic table, which contains 118 elements. |