The periodic table has developed hugely over the last 180 years. Many different theories and ideas were come up with in order to try and discover how the elements all fitted together.

In 1780, Johann Wolfgang Döbereiner was born. He apprenticed under an apothecary and took an interest in Chemistry. He attended many lectures and eventually become a professor at the University of Jena in Germany, in 1810.

During his time at the University, Döbereiner started to take an interest in relationships between the elements. In 1829 he discovered trends in some properties of select groups of elements. He thought that the elements should be grouped into threes by the similarities in their properties.
For example, the average atomic mass of Lithium and Potassium was similar to the atomic mass of Sodium. Döbereiner also found similar patterns in calcium, barium and strontium as well as chlorine, bromine and iodine and tellurium, sulphur and selenium. These were called triads of elements, and were known as “Döbereiner’s Triads” after their inventor.

Almost 40 years later, an Englishman named John Newlands started to look into the table of elements. He was the first person to arrange the Periodic Table of Elements in order of their relative atomic weights. Newlands studied Döbereiner’s theory on triads in the periodic table, and continued his work. In 1865 John published a book called “Law of Octaves” in which he states “any given element will exhibit analogues behaviour to the eighth element following it in the table". Newland arranged the elements in order of atomic weights that were known at that time. They were arranged in 7 groups, which he likened to the octaves of music. He numbered them sequentially to show the order of atomic weights. In Newland’s table, periods and groups are shown going down and across which is the opposite from the modern periodic table we know today.

Dmitri Mendeleev was the creator of the periodic table as we know it today. Born in 1834 in Siberia, he grew up in a large family. After his father passed away and his mother’s factory burnt, the Mendeleev family became poor and was forced to move to Russia. In 1864 he became a professor at the Saint Petersburg Technological Institute and then the Saint Petersburg State University in 1865.
After becoming a teacher, Mendeleev wrote the definitive textbook of his time “Principles of Chemistry”. He attempted to classify the elements according to their chemical properties and he noticed several patterns which led him to suggest his own version of the Periodic Table.

On March the 6th 1869, Dmitri Mendeleev made a formal presentation to the Russian Chemistry Society, called “The Dependence between the Properties of the Atomic Weights of the Elements”. This presentation described the elements according to atomic weight and valence.
Mendeleev’s presentation said that “The elements, if arranged in according to their atomic weight, exhibit an apparent periodicity of properties.” He also stated that “We must expect the discovery of many yet unknown elements–for example, two elements, analogous to aluminium and silicon, whose atomic weights would be between 65 and 75.” He predicted there were many elements that were yet to be discovered, and so he left space for them in his table. Most people dismissed Mendeleev for thinking there would be more elements however he was proven right in both 1875 and 1886 when Gallium and Germanium were found, respectively.

Dmitri Mendeleev is today credited for the creation of the Periodic Table, and in 1906 was recommended for the Nobel Prize in Chemistry, though he did not get it. Several other elements have been discovered since his death and all fit perfectly into his design of the Periodic Table of Elements.