History of the Periodic Table

The first step in the creation of the Periodic table was in 1789 when French chemist Antoine Lavoisier grouped the elements as gases, non-metals, metals and earths. 40 years later, German physicist Johann Wolfang Döbereiner noticed similarities in the physical and chemical properties of certain elements. This lead him to arrange elements in groups of three and in increasing atomic mass, he called them triads. He observed that some properties of the middle elements, such as the atomic mass and density was roughly the average of the properties of the other two elements in the triads.

The next big stepping stone came with the first international conference of chemistry in Karlsruhe, Germany, in 1860. It was concluded that hydrogen would be assigned the atomic mass of 1 and the atomic mass of other elements would be decided by their comparison with hydrogen. For example, Oxygen, being 16 times heavier than hydrogen, would have an atomic weight of 16.

Next came the law of octaves in which English chemist John Newlands arranged the elements into a table with increasing order of atomic masses. Newlands found that every eight elements had similar properties and this was the law of octaves. He arranged the elements in eight groups but left no gaps for undiscovered elements.

The final step in the Periodic Table came in 1869, renowned Russian chemist Dmitri Mendeleev created the table that became the modern periodic table, leaving gaps for elements that were yet to be discovered. He arranged them according to their atomic weight and if an element did not fit the group he would rearrange the groups. Mendeleev predicted the properties of some then undiscovered elements and gave them names such as "eka-aluminium" as it was an element with properties similar to aluminium. Later eka-aluminium was discovered as gallium.