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  2. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    Today, 118 elements are known, the first 94 of which are known to occur naturally on Earth at present. [10] [a] The remaining 24, americium to oganesson (95–118), occur only when synthesized in laboratories. Of the 94 naturally occurring elements, 83 are primordial and 11 occur only in decay

  3. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    Chemical elements may also be categorized by their origin on Earth, with the first 94 considered naturally occurring, while those with atomic numbers beyond 94 have only been produced artificially via human-made nuclear reactions. Of the 94 naturally occurring elements, 83 are considered primordial and either stable or weakly

  4. Plutonium - Wikipedia

    en.wikipedia.org/wiki/Plutonium

    Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen.

  5. List of chemical elements - Wikipedia

    en.wikipedia.org/wiki/List_of_chemical_elements

    List of chemical elements. 118 chemical elements have been identified and named officially by IUPAC. A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [1]

  6. Preon - Wikipedia

    en.wikipedia.org/wiki/Preon

    Preon theory is motivated by a desire to replicate in particle physics the achievements of the periodic table in Chemistry, which reduced 94 naturally occurring elements to combinations of just three building-blocks (proton, neutron, electron).

  7. List of nuclides - Wikipedia

    en.wikipedia.org/wiki/List_of_nuclides

    There are 251 known so-called ... Bismuth-209 is notable as it is the only naturally occurring isotope of an element which was ... 94: 148: 7.845 218: 1.183 ...

  8. Discovery of chemical elements - Wikipedia

    en.wikipedia.org/wiki/Discovery_of_chemical_elements

    McMillan and Abelson found that 239 93 itself undergoes beta decay and must produce an isotope of element 94, but the quantities they used were not enough to isolate and identify element 94 along with 93. [176] Natural traces were found in Belgian Congo pitchblende by D. F. Peppard et al. in 1952. [177] 85 Astatine: 1940

  9. Isotope - Wikipedia

    en.wikipedia.org/wiki/Isotope

    Thus, about two-thirds of stable elements occur naturally on Earth in multiple stable isotopes, with the largest number of stable isotopes for an element being ten, for tin (50 Sn). There are about 94 elements found naturally on Earth (up to plutonium inclusive), though some are detected only in very tiny amounts, such as plutonium-244.