![]() The main value of the periodic table is the ability to predict the chemical properties of an element based on its location on the table. Production of additional synthetic elements beyond atomic number 118 is being pursued their properties are expected to continue the periodic patterns shown by the presently known elements. Numerous synthetic radionuclides of various naturally occurring elements have also been produced. While plutonium is now included among the regularly occurring natural elements, and technetium, promethium, and neptunium also occur naturally, but only incidentally, these four elements were first identified and characterized from technologically produced samples. No gaps remain in the current 118-element periodic table, since all of the 91 regularly occurring chemical elements have now been isolated, characterized, and named, and technetium, promethium, and all of the transuranic elements through 118 have been synthesized. One of the strengths of Mendeleev’s original presentation was the prediction of the properties of then-undiscovered elements expected to fill noticeable gaps in the arrangement, such as his “eka-aluminium” with properties intermediate between aluminium and indium, which was discovered in 1875 and named gallium. ![]() Its principles are especially important in chemical engineering. The table has found many applications not only in chemistry and physics, but also in such diverse fields as geology, biology, materials science, engineering, agriculture, medicine, nutrition, environmental health, and astronomy. Since the periodic table powerfully predicts the abilities of various elements to combine into chemical compounds, use of the periodic table is now ubiquitous within the academic discipline of chemistry, providing a useful framework to classify, systematize, and compare all of the many different forms of chemical behavior. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behavior. The extended periodic table adds the 8th and 9th periods, incorporating the f-block and adding the theoretical g-block.Įlement categories in the periodic table MetalsĪtomic number colors show state of matter at standard conditions (0 ☌ and 1 atm): Solidsīorders show natural occurrence: PrimordialĪlthough there were precursors to this tabular presentation, its invention is generally credited to Russian chemist Dmitri Mendeleev, who developed a version of the now-familiar tabular presentation in 1869 to illustrate recurring (“periodic”) trends in the properties of the then-known elements. The wide periodic table incorporates the f-block. This common arrangement of the periodic table separates the lanthanides (lanthanoids) and actinides (actinoids) (the f-block) from other elements. The following presentation of the periodic table includes links to Wikipedia articles on each of the 118 included elements: Group # While rectangular in general outline, counter-intuitive gaps are included in the horizontal rows ( “periods”) as needed to keep elements with similar properties together in each vertical column ( “group”), such as the alkali metals, the alkali earths, the halogens, and the noble gases. Elements are presented in the periodic table by increasing values of their atomic numbers, the number of protons in their atomic nuclei. The periodic table (or, more formally, the periodic table of the elements or periodic table of the chemical elements) is a tabular display organizing the 118 known chemical elements by selected properties of their atomic structure.
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