Periodic table centre and the transition metals, lanthanides, and actinides occupying peninsulas. Most periodic tables are two-dimensional; three-dimensional tables are known to as far back as at least 1862 (pre-dating Mendeleev's two-dimensional table of 1869). More recent examples include Courtines' Periodic Classification (1925), Wringley's Lamina System (1949), Giguère's Periodic helix (1965) and Dufour's Periodic Tree (1996). Going one further, Stowe's Physicist's Periodic Table (1989) has been described as being four-dimensional (having three spatial dimensions and one colour dimension). The various forms of periodic tables can be thought of as lying on a chemistry–physics continuum. Towards the chemistry end of the continuum can
Alternative periodic tables each element has with respect to another element in the table. Other tables aim to emphasize the chemical element isolations by humans over time. Charles Janet's Left step periodic table (1928) is considered to be the most significant alternative to the traditional depiction of the periodic system. It organizes elements according to orbital filling (instead of valence) and is widely used by physicists. Compared to the common layout, the Left step table has these changes: A modern version of the periodic table is constructed by Valery Tsimmerman, named the ADOMAH periodic table (2006). Its structure is based on the four