The periodic table represents the discovery of the elements over time and their attributes

elements discovered
Antiquity to Middle Ages
Unrecorded discoveries up into the Middle Ages
Middle Ages–​1799
Age of enlightenment
1800–​1849
Scientific and industrial revolutions
1850–​1899
The age of classifying elements
1900–​1949
Development of quantum theory
1950–​present
Development of synthetic elements