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National Periodic Table Day is observed annually on February 7.
To understand the development of the periodic table, we first must understand the discovery of elements and their effect on science.
Elements known to ancient man were few. Gold, silver, copper, iron, lead, tin, mercury, sulfur and carbon were the earliest known elements. These were all known prior to the 1st century A.D.
Over time, arsenic, antimony, phosphorus and zinc were discovered. By 1809 there were 47 discovered elements.
One of the earliest attempts to organize the elements was by Johann Döbereiner in 1817. He organized elements into groups of three, or triads, based on similar qualities.
On February 7, 1863, English chemist John Newlands published one of the first table of elements, which divided the known 56 elements into 11 groups based on the “Law of Octaves.” This suggested that any one element will have similar properties to elements eight places before and behind it on the table.
Arranging the elements according to increasing atomic weight, Newlands was one of the first scientists to detect a pattern to the properties of elements. As a result, his table left room for new discoveries, predicting future discovered elements would complete the table. Newlands correctly predicted the discovery of Germanium.
While parts of Newlands periodic table had flaws, so did other later proposed tables. In 1869 chemist Dimitri Mendeleev published a paper developing a periodic table arranging the elements also based on atomic mass. By this time only 60 of the over 100 elements we know today were discovered.
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