The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic ...

The first periodic table to become generally accepted was that of the Russian chemist Dmitri Mendeleev in 1869: he formulated the periodic law as a dependence of chemical properties on atomic mass.

Mrs Roberts: Well, the modern periodic table shows us all of the elements arranged in rows, which are called periods. It has changed a lot over the years as we've learned more and more about atoms.