In the 1920s, who created the Left-Step Periodic Table (LSPT) of the chemical elements, basing the positions of the elements on patterns in the arrangement of electrons around the atomic nucleus?

Explanation

Charles Janet developed the left-step arrangement of the periodic table in the 1920s. The layout groups elements in a sequence closely related to electronic structure and orbital filling. It is an alternative representation of the same elements rather than a claim that the modern periodic table has only one valid graphical layout.