Although elements such as gold, silver, tin, copper, lead and mercury have been known since earliest times, the first scientific discovery of an element occurred in 1649. Hennig Brand, a German alchemist, treated urine to a series of processes that resulted in the production of the element phosphorus.
Over the next 200 years, a great deal of knowledge about elements and compounds was gained. By the middle of the 19th century, about 60 elements had been discovered.
Scientists began to recognise patterns in the properties of these elements and set about developing classification schemes.
French geologist Alexandre-Emile Béguyer de Chancourtois listed the elements on paper tape and wound them, spiral like, around a cylinder. Certain ‘threes’ of elements with similar properties came together down the cylinder. He called his model the ‘telluric screw’.
English chemist John Newlands noticed that, if the elements were arranged in order of atomic weight, there was a periodic similarity every 8 elements. He proposed his ‘law of octaves’ on this.
Lothar Meyer complied a periodic table of 56 elements based on a regular repeating pattern of physical properties such as molar volume. Once again, the elements were arranged in order of increasing atomic weights.
Russian chemist Dmitri Mendeleev produced a periodic table based on atomic weights but arranged ‘periodically’. Elements with similar properties appeared under each other. Gaps were left for yet to be discovered elements.
William Ramsay discovered the noble gases and realised that they represented a new group in the periodic table.
Henry Moseley determined the atomic number of each of the known elements. He realised that, if the elements were arranged in order of increasing atomic number rather than atomic weight, they gave a better fit within the ‘periodic table’.
Glenn Seaborg artificially produced heavy mass elements such as neptunium. These new elements were part of a new block of the periodic table called ‘actinides’.
The periodic table today
Most school science laboratories have a copy of the periodic table pinned to a wall somewhere.
Close inspection of the table shows the following distribution of types of element.
Most of the elements are metals. Metalloids are elements that have some of the physical properties of metals but some of the chemical properties of non-metals. Antimony, for example, conducts electricity but its chemistry resembles that of the non-metal phosphorus.
Scientists are constantly working on discovering new materials and further investigating the properties of existing elements. The periodic table can be reviewed and new elements can be added, but only added after rigorous scientific examination. The International Union of Pure and Applied Chemistry (IUPAC) verifies the additions of new elements and at the end of 2015 the 7th period of the periodic table of elements was completed.
Nature of science
Science is a blend of logic and imagination. In the development of the periodic table of the elements, Mendeleev demonstrated these attributes.
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The International Union of Pure and Applied Chemistry (IUPAC) website.
Official announcement of the discovery and assignment of new elements with atomic numbers 113, 115, 117 and 118 in 2015.
BBC news article about the 4 new elements that was announced on 30 December 2015.