We created a timeline of the history of the periodic table. The Periodic Table has constantly been improved and developed over the past 200 years, but in 1869 Dimitri Mendeleev finished the first version of the periodic table as we know it today, by arranging the elements by atomic mass and leaving spaces open for the elements that were not yet discovered. ![]() Who invented the Periodic Table of Elements? The periodic table also gives us an idea of what the characteristics of an element might be and help us predict how an element might react based on in which group it is located. (credit a: modification of work by Serge Lachinov credit b: modification of work by Den fjättrade ankan/Wikimedia Commons) By the twentieth century, it became apparent that the periodic relationship involved atomic numbers. The Periodic Table of Elements can be used as an assisting tool in chemical calculations, when a specification of an element is needed it is easily found in the Periodic Table. Figure 2.25 (a) Dimitri Mendeleev is widely credited with creating (b) the first periodic table of the elements. How is the Periodic Table of Elements used? The table lists all the elements that are currently known (118), in descending order of the number of protons that are present, in a single atom of the element. The Periodic table of elements is a tool, developed by scientists over hundreds of years. ![]() These are usually taken to be scandium, 21, to zinc, 30 (the iron-group transition metals) yttrium, 39, to cadmium, 48 (the palladium-group transition metals) and hafnium, 72, to mercury, 80 (the platinum-group transition metals). List of all the elements and their properties: A number of the elements of each long period are called the transition metals. For elements with no stable isotopes, the mass number of the isotope with the longest half-life is in parentheses.
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