How We Came Up With the Periodic Table

  The periodic table not only gave nightmares to former chemistry students but also revolutionized the entire field of chemistry, allowing scientists to discern whether or not there were undiscovered elements and how to categorize these yet undiscovered elements (To the pain of chemistry students). A scientist named Professor Mendeleev was working on the puzzle. Before the periodic table, scientists found that if you listed elements in order of their atomic weights, every eighth element would cause a new reaction. However, there were gaps, and the entire theory fell apart after the twentieth element. Mendeleev came up with the idea to rearrange the list into a table, leaving gaps for undiscovered elements. Everything fit neatly into place, and as new elements were discovered, the table became more and more filled out until it became the periodic table we know and hate today.