Periodic Table = a table of the chemical elements arranged in order of atomic number
The elements are placed according to their atomic number, the arrangement of each atom’s electrons and recurring chemical properties.
Russian chemist Dmitri Mendeleev published the first recognizable periodic table in 1869, developed mainly to illustrate periodic trends of the then-known elements.
To commemorate this, the United Nations has designated 2019 as the International Year of the Periodic Table.
Hidden histories – New Yorker