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  2. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    Elements in the same group tend to show similar chemical characteristics. Vertical, horizontal and diagonal trends characterize the periodic table. Metallic character increases going down a group and from right to left across a period. Nonmetallic character increases going from the bottom left of the periodic table to the top right.

  3. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    The radius varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighboring atoms (coordination number) and a quantum mechanical property known as spin. [70] On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to ...

  4. List of chemical elements - Wikipedia

    en.wikipedia.org/wiki/List_of_chemical_elements

    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 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...

  5. Table of nuclides - Wikipedia

    en.wikipedia.org/wiki/Table_of_nuclides

    A chart or table of nuclides maps the nuclear, or radioactive, behavior of nuclides, as it distinguishes the isotopes of an element.It contrasts with a periodic table, which only maps their chemical behavior, since isotopes (nuclides that are variants of the same element) do not differ chemically to any significant degree, with the exception of hydrogen.

  6. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    Thus, magnesium-24 (24 is the mass number) is an atom with 24 nucleons (12 protons and 12 neutrons). Whereas the mass number simply counts the total number of neutrons and protons and is thus an integer, the atomic mass of a particular isotope (or "nuclide") of the element is the mass of a single atom of that isotope, and is typically expressed ...

  7. Lewis structure - Wikipedia

    en.wikipedia.org/wiki/Lewis_structure

    The nitrogen atom has only 6 electrons assigned to it. One of the lone pairs on an oxygen atom must form a double bond, but either atom will work equally well. Therefore, there is a resonance structure. Tie up loose ends. Two Lewis structures must be drawn: Each structure has one of the two oxygen atoms double-bonded to the nitrogen atom.

  8. Periodic trends - Wikipedia

    en.wikipedia.org/wiki/Periodic_trends

    The ionization energy is the minimum amount of energy that an electron in a gaseous atom or ion has to absorb to come out of the influence of the attracting force of the nucleus. It is also referred to as ionization potential. The first ionization energy is the amount of energy that is required to remove the first electron from a neutral atom.

  9. Isobar (nuclide) - Wikipedia

    en.wikipedia.org/wiki/Isobar_(nuclide)

    In this chart of nuclides, isobars occur along diagonal lines running from the lower right to upper left.The line of beta stability includes the observationally stable nuclides shown in black; disconnected 'islands' are a consequence of the Mattauch isobar rule.