On February 7th, National Periodic Table Day recognizes the publication of the first table of elements and how it has changed over the years.
To understand the development of the periodic table, we first must understand the discovery of elements and their effect on science. Ancient man knew of few elements. By the 1st century A.D., mankind knew about the elements of gold, silver, copper, iron, lead, tin, mercury, sulfur, and carbon. Over time, we added arsenic, antimony, phosphorus, and zinc to our discoveries. By 1809, there were 47 discovered elements.
Johann Döbereiner made one of the earliest attempts to organize the elements 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. Newlands divided the known 56 elements into 11 groups based on the “Law of Octaves.” His table 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 and predicting future discovered elements would complete the table. In fact, Newlands correctly predicted the discovery of Germanium.
While parts of Newlands’ periodic table contained flaws, so did other later proposed tables. In 1869, chemist Dimitri Mendeleev published a paper developing a new periodic table. Mendeleev’s table also arranged the elements based on atomic mass. By this time, only 60 of the over 100 elements we know today were discovered.
As on previous tables, inaccuracies were attributed to some of those elements. While Mendeleev corrected some of these inaccuracies, he didn’t correct them all. Mendeleev made assumptions about others causing elements to be placed incorrectly on the table. Like Newlands, Mendeleev also predicted discoveries, and he correctly predicted the properties of five elements and their compounds.
The discoveries throughout Scot William Ramsay’s career from 1892 to 1910, along with John William Strutt, Morris Travers and Frederick Soddy led to the identification of the noble gasses. In 1904, the Nobel Prize was awarded to Ramsay for discovering five elements.
Henry Moseley, an experimental physicist, contributed to the development of the modern periodic table. In 1913, Moseley discovered that each element has a specific number of protons. As a result, four new chemical elements were later found, though not during his lifetime.
Since the early 20th century, the periodic table remains largely unchanged. However, the 21st century is still young. Some researchers suggest new approaches to the periodic table while maintaining its integrity as one of the most valuable tools in the science of chemistry. The current table tallies a total of 118 elements.