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  2. Helium - Wikipedia

    en.wikipedia.org/wiki/Helium

    'sun') is a chemical element; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert , monatomic gas and the first in the noble gas group in the periodic table . [ a ] Its boiling point is the lowest among all the elements , and it does not have a melting point at standard pressures.

  3. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    The first periodic table to become generally accepted was that of the Russian chemist Dmitri Mendeleev in 1869; he formulated the periodic law as a dependence of chemical properties on atomic mass. As not all elements were then known, there were gaps in his periodic table, and Mendeleev successfully used the periodic law to predict some ...

  4. List of chemical elements - Wikipedia

    en.wikipedia.org/wiki/List_of_chemical_elements

    Like the periodic table, the list below organizes the elements by the number of protons in their atoms; it can also be organized by other properties, such as atomic weight, density, and electronegativity. For more detailed information about the origins of element names, see List of chemical element name etymologies.

  5. This 12-year-old memorized the periodic table at age 2. He’s ...

    www.aol.com/12-old-memorized-periodic-table...

    The gifted tween, who memorized the periodic table at 2 years old and has taught lectures at colleges in India since he was 7, graduated on Wednesday from Malverne High School in Nassau County, ...

  6. Noble gas - Wikipedia

    en.wikipedia.org/wiki/Noble_gas

    They were once labeled group 0 in the periodic table because it was believed they had a valence of zero, meaning their atoms cannot combine with those of other elements to form compounds. However, it was later discovered some do indeed form compounds, causing this label to fall into disuse.

  7. History of the periodic table - Wikipedia

    en.wikipedia.org/wiki/History_of_the_periodic_table

    Bohr acknowledged that he was influenced by the work of Walther Kossel, who in 1916 was the first to establish an important connection between the quantum atom and the periodic table. He noticed that the difference between the atomic numbers 2, 10, 18 of the first three noble gases, helium, neon, argon, was 8, and argued that the electrons in ...

  8. List of elements by atomic properties - Wikipedia

    en.wikipedia.org/wiki/List_of_elements_by_atomic...

    This is a list of chemical elements and their atomic properties, ordered by atomic number (Z).. Since valence electrons are not clearly defined for the d-block and f-block elements, there not being a clear point at which further ionisation becomes unprofitable, a purely formal definition as number of electrons in the outermost shell has been used.

  9. Main-group element - Wikipedia

    en.wikipedia.org/wiki/Main-group_element

    The periodic table of the chemical elements.The columns represent the groups.Groups 1, 2 and 13 to 18 constitute the main group. Sometimes groups 3 and 12, as well as the lanthanides and actinides (the two rows at the bottom), are also included in the main group.

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