History of the Periodic Table

Many people worked hard to create the Periodic Table of Elements, though only one person received most of the credit. Scientists continue to add to and alter the design today.

The first person to make a periodic table was a German chemist named J.W. Dobereiner. In 1829, he grouped the elements into triads of similar properties. He also tried to group the elements into octaves based on similar properties, but both of his tables failed because not all of the elements could be grouped into triads or octaves. 

The next periodic table was developed in 1862 by a French geologist named Alexander Béguyer de Chancourtois. He tried to make a 3-D diagram with the elements outside of a cylinder, with every 360-degree turn, including an element of an increased atomic weight of 16 or higher. He called this the Telluric Screw, but few people learned of its existence. 

In 1865, an Englishman named John Newlands attempted to make a table. He grouped his elements by eight, but sometimes crammed two elements with the same properties in the same box. Because his work was inconsistent, it was not published by the Royal Society of Chemistry. It wasn't until 1998 that he got credit for what he did.

The design of the periodic table that we use today was made by Dmitri Mendeleev. In February 1869, he created what he called the Periodic System or Periodic Table of Elements as we know it. He wrote each element on cards and arranged them in order of increasing atomic weight. He left spaces for elements he thought existed, but weren't discovered yet such as 21 (Scandium), 31 (Gallium), and 32 (Germanium). These elements were detected after Mendeleev's table was developed. His predictions for the elements were very close to what scientists found when they identified them years later.

Another German chemist, Julius Lothar Meyer, was also working on a periodic table. He might have met Mendeleev, but they were unaware of each other’s work. Meyer produced several versions of his periodic table between the years of 1864-1870. The first was made in 1864, where he grouped only 28 elements by valency (how many other atoms they can combine with). His second table had valency grouped in vertical lines and included the transitional metals. His last was very similar to Mendeleev's table but it wasn't published until 1870, a year after Mendeleev's. Meyer did concede that Mendeleev's came first, however. 

Between the years of 1911 and 1913, an English chemist, Henry Moseley, x-rayed all of the elements. He arranged the elements by their frequency and assigned them an atomic number.  Contributed to the start of the periodic table we use today, the pattern that was found earlier by Mendeleev was made without switching the elements around. He discovered the periodic law for making the table: when elements are placed in order of increasing atomic number, there is a pattern in their chemical and physical properties.

For almost 100 years, many scientists contributed their work to produce a periodic table that is very useful for people today. Although it has changed throughout time, the way it is composed has stayed largely the same.

[Sources: science.howstuffworks.com; www.rsc.org]